[composer] Ignore locked items when using move item content tool. Keeps a
consistent behaviour with the move/resize item tool, and allows for
moving item content for maps which are stacked below locked items.
[composer] Fix ctrl modifier not applying to wheel events when in move item
content mode, add missing undo merge command for item zoom (refs #7974)
[composer] Ignore null field values or expressions which result in null
when evaluating data defined settings
[composer] Don't disable widgets accompanying data defined controls when there's no need to
[composer] Default to 30 visible rows for table items, increase maximum number of rows to 99999 (fix #11284)