remove core key

Unused use statements, not using StringTranslationTrait, array square brackets, unused variable, missing member variable doc comment, end of file lines

Closes #3501868

css/cards.css

+.card {
+  position: relative;
+  display: -ms-flexbox;
+  display: flex;
+  -ms-flex-direction: column;
+  flex-direction: column;
+  min-width: 0;
+  word-wrap: break-word;
+  background-color: #fff;
+  background-clip: border-box;
+  border: 1px solid rgba(0, 0, 0, 0.125);
+  border-radius: 0.25rem;
+}
+
+.card > hr {
+  margin-right: 0;
+  margin-left: 0;
+}
+
+.card > .list-group {
+  border-top: inherit;
+  border-bottom: inherit;
+}
+
+.card > .list-group:first-child {
+  border-top-width: 0;
+  border-top-left-radius: calc(0.25rem - 1px);
+  border-top-right-radius: calc(0.25rem - 1px);
+}
+
+.card > .list-group:last-child {
+  border-bottom-width: 0;
+  border-bottom-right-radius: calc(0.25rem - 1px);
+  border-bottom-left-radius: calc(0.25rem - 1px);
+}
+
+.card > .card-header + .list-group,
+.card > .list-group + .card-footer {
+  border-top: 0;
+}
+
+.card-body {
+  -ms-flex: 1 1 auto;
+  flex: 1 1 auto;
+  min-height: 1px;
+  padding: 1.25rem;
+}
+
+.card-title {
+  margin-bottom: 0.75rem;
+}
+
+.card-subtitle {
+  margin-top: -0.375rem;
+  margin-bottom: 0;
+}
+
+.card-text:last-child {
+  margin-bottom: 0;
+}
+
+.card-link:hover {
+  text-decoration: none;
+}
+
+.card-link + .card-link {
+  margin-left: 1.25rem;
+}
+
+.card-header {
+  padding: 0.75rem 1.25rem;
+  margin-bottom: 0;
+  background-color: rgba(0, 0, 0, 0.03);
+  border-bottom: 1px solid rgba(0, 0, 0, 0.125);
+}
+
+.card-header:first-child {
+  border-radius: calc(0.25rem - 1px) calc(0.25rem - 1px) 0 0;
+}
+
+.card-footer {
+  padding: 0.75rem 1.25rem;
+  background-color: rgba(0, 0, 0, 0.03);
+  border-top: 1px solid rgba(0, 0, 0, 0.125);
+}
+
+.card-footer:last-child {
+  border-radius: 0 0 calc(0.25rem - 1px) calc(0.25rem - 1px);
+}
+
+.card-header-tabs {
+  margin-right: -0.625rem;
+  margin-bottom: -0.75rem;
+  margin-left: -0.625rem;
+  border-bottom: 0;
+}
+
+.card-header-pills {
+  margin-right: -0.625rem;
+  margin-left: -0.625rem;
+}
+
+.card-img-overlay {
+  position: absolute;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  left: 0;
+  padding: 1.25rem;
+  border-radius: calc(0.25rem - 1px);
+}
+
+.card-img,
+.card-img-top,
+.card-img-bottom {
+  -ms-flex-negative: 0;
+  flex-shrink: 0;
+  width: 100%;
+}
+
+.card-img,
+.card-img-top {
+  border-top-left-radius: calc(0.25rem - 1px);
+  border-top-right-radius: calc(0.25rem - 1px);
+}
+
+.card-img,
+.card-img-bottom {
+  border-bottom-right-radius: calc(0.25rem - 1px);
+  border-bottom-left-radius: calc(0.25rem - 1px);
+}
+
+.card-deck .card {
+  margin-bottom: 15px;
+}
+
+@media (min-width: 576px) {
+  .card-deck {
+    display: -ms-flexbox;
+    display: flex;
+    -ms-flex-flow: row wrap;
+    flex-flow: row wrap;
+    margin-right: -15px;
+    margin-left: -15px;
+  }
+  .card-deck .card {
+    -ms-flex: 1 0 0%;
+    flex: 1 0 0%;
+    margin-right: 15px;
+    margin-bottom: 0;
+    margin-left: 15px;
+  }
+}
+
+.card-group > .card {
+  margin-bottom: 15px;
+}
+
+@media (min-width: 576px) {
+  .card-group {
+    display: -ms-flexbox;
+    display: flex;
+    -ms-flex-flow: row wrap;
+    flex-flow: row wrap;
+  }
+  .card-group > .card {
+    -ms-flex: 1 0 0%;
+    flex: 1 0 0%;
+    margin-bottom: 0;
+  }
+  .card-group > .card + .card {
+    margin-left: 0;
+    border-left: 0;
+  }
+  .card-group > .card:not(:last-child) {
+    border-top-right-radius: 0;
+    border-bottom-right-radius: 0;
+  }
+  .card-group > .card:not(:last-child) .card-img-top,
+  .card-group > .card:not(:last-child) .card-header {
+    border-top-right-radius: 0;
+  }
+  .card-group > .card:not(:last-child) .card-img-bottom,
+  .card-group > .card:not(:last-child) .card-footer {
+    border-bottom-right-radius: 0;
+  }
+  .card-group > .card:not(:first-child) {
+    border-top-left-radius: 0;
+    border-bottom-left-radius: 0;
+  }
+  .card-group > .card:not(:first-child) .card-img-top,
+  .card-group > .card:not(:first-child) .card-header {
+    border-top-left-radius: 0;
+  }
+  .card-group > .card:not(:first-child) .card-img-bottom,
+  .card-group > .card:not(:first-child) .card-footer {
+    border-bottom-left-radius: 0;
+  }
+}
+
+.card-columns .card {
+  margin-bottom: 0.75rem;
+}
+
+@media (min-width: 576px) {
+  .card-columns {
+    -webkit-column-count: 3;
+    -moz-column-count: 3;
+    column-count: 3;
+    -webkit-column-gap: 1.25rem;
+    -moz-column-gap: 1.25rem;
+    column-gap: 1.25rem;
+    orphans: 1;
+    widows: 1;
+  }
+  .card-columns .card {
+    display: inline-block;
+    width: 100%;
+  }
+}
+
+.accordion > .card {
+  overflow: hidden;
+}
+
+.accordion > .card:not(:last-of-type) {
+  border-bottom: 0;
+  border-bottom-right-radius: 0;
+  border-bottom-left-radius: 0;
+}
+
+.accordion > .card:not(:first-of-type) {
+  border-top-left-radius: 0;
+  border-top-right-radius: 0;
+}
+
+.accordion > .card > .card-header {
+  border-radius: 0;
+  margin-bottom: -1px;
+}