Remove Shift+F4 shortcut key for cell reference and add it to the OOo
Legacy compatibility mode. Improve wording of cell reference error
message. Unify shortcut for Data Sources to Ctrl + Shift + F4.

Change-Id: I0f4ab3768d2663984bb294763c2e4b299c5e8186
Reviewed-on: https://gerrit.libreoffice.org/22803Reviewed-by: Yousuf Philips <philipz85@hotmail.com>
Tested-by: Yousuf Philips <philipz85@hotmail.com>