- Made the calendar module accept a $date parameter such that you
  can jump directly to a certain date in the archives.  Also made
  the calendar link to itself such that it is self-contained.

- Code beautifications: quoted a lot of arrays, removed dead code
  and simplified a few things.

- Replaced the Calendar class by one function "calendar_display":
  using a class (or class instance, or object) doesn't make sense
  in the archives' case.

- Renamed "calendar.module" to "archive.module".

- Fixed a /problem/ with node settings not always being saved like
  expected.

- Reorganized the user menu: renamed a couple of links for clarity
  and structure.

- Fixed a few typos.