Clear bookmarks and index on journal deletion
Update page number when bookmark is moved to a different page
Implement saving/opening of bookmarks into the XOJ
Bookmark column headers clickable/sortable. Sorts by page number by
default.
Sorting of bookmarks within a page
Prevent bookmarks from being deleted from the canvas.
Default bookmark name + "Enter" key in GtkEntry accepts dialog
Editing of bookmark names
Toolbar item for creating bookmarks + creation of bookmarks relative to
current scroll location
Code cleanup
Merge branch 'bookmarks'

Conflicts:
	src/xo-callbacks.h
	src/xo-misc.c