Delete bookmarks in all buffers #24
Description
Add new command :ClearAllBookmarks
Add new shortcut: mx
When clearing all bookmarks the user might have forgotten about signs in other buffers. Therefore we should ask him if he really wants to delete them:
Do you really want to delete {N} bookmarks in {M} buffers? (y/n)
This should only happen if there are bookmarks in other buffers than the current one. Also the user should be able to disable the warning: bookmark_clear_all_warn = 0