Merged be.doc documentation rewrite + bugfixes + new bugs

Highlights:
  * Fix broken Diff.comment_body_change_string implementation.
  * Fix List --severity handling, added --important
  * Fix `be target --help`
  * Fix non-text/plain `be comment` code and added 'Created
    comment...' output

diff --cc NEWS
index e0dc81caba9cb52ec7016ee705945343f2e43875,d5d63e4c81f8061e4530bb6403f1f64d9348e9f2..7ff2c43f7a95c2899f75f56fae69922fe7bcbfed
--- 1/NEWS
--- 2/NEWS
+++ b/NEWS
@@@ -1,5 -1,6 +1,6 @@@
  January 23, 2010
-  * Added `be list --mine`, listing bugs belonging to you.
+  * Added 'Created comment with ID .../.../...' output to `be comment`.
 - * Added --important severity shortcut to `be list`.
++ * Added --important and --mine to `be list`.
  
  January 20, 2010
   * Renamed 'be-mbox-to-xml' -> 'be-mail-to-xml' and added support for