Try to finally fix #6930. All the paths that did not come from context

Try to finally fix #6930. All the paths that did not come from context
menus were (intentionally) missing, and it turns out they were needed.

Normally all invocations of INSET_MODIFY should trigger a recordUndo now.
Of course all cases have not been tested, but it should be working.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@36770 a592a061-630c-0410-9148-cb99ea01b6c8