Add missing include file

This fixes the build on Windows
Include GDK headers in inf-gtk-permissions-dialog.c
Fix erase-text propagation in InfTextFixlineBuffer
Add support for unknown notes in InfdDirectory
Add infd_directory_remove_plugin() function
Turn note plugins into regular plugins
Fix use of uninitialized variable in inf_text_gtk_view_user_invalidate_user_area

The bug manifests itself when show_remote_cursors and show_remote_selections
evaluate to FALSE and show_remote_current_lines evaluates to TRUE.

Usual symptoms are crashes.
Expand server's document list on connect
Implement inf_gtk_browser_store_remove_browser
Fix g_return_val_if_fail in infd_directory_remove_plugin()
Merge remote-tracking branch 'polarina/master'
Added some code for handling of renaming nodes.
Merge branch 'master' of git://git.0x539.de/git/infinote