improved list handling

Ignore-this: 2e4f3fbfb28917ee66cf3e1925c806d3

This patch adds multiple enhancements to handling lists and indented
code blocks in the editor.

1. Pressing enter when in a list item or code block will keep the indention
   and adds a new list point
2. Pressing space at the start of a list item will indent the item to the
   next level
3. Pressing bckspace at the start of a list item will outdent the item
   to the previous level or delete the list bullet when you are at the
   1st level already
4. A new type of formatting button called formatln is added. It applies
   formatting to several lines. It's used for the list buttons currently
   and makes it possible to convert mutiple lines to a list

This enhncement are currently only tested in Firefox are most likely to
break IE compatibility. A compatibility patch will be submitted later

note: development was part of the ICKE 2.0 project see
      http://www.icke-projekt.de for info

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