HIG: Miscellaneous improvements to Line Numbering dialog

* Add colons for labels that precede colons (fdo#78826)
* Sentence capitalization
* More concise label for fdo#84504
* Disable nonsensical manual resizing
* The usual XML dance caused by saving the file with newer Glade.

Change-Id: I3b8a6d5d915c2c6cfb4cf0960f5d59bc644d4994
Reviewed-on: https://gerrit.libreoffice.org/11869
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>