[#3436455] Fix insert_media after upgrades to Insert to make it work with CKEditor.

• Fix an issue in Insert.js where the click event isn't halted, which can cause the media widget's remove button to get clicked.
• Refactor insert_media to use appropriate hooks
• Add 3rd parameter, $insertElement, to hook_insert_render() to accomodate multi-value media fields.

Closes #3436455