Don't try to get newtimestamp from edit if no change was made

ApiEditPage can give us 'nochange' instead of the
'oldrevid'/'newrevid'/'newtimestamp' keys if we gave it a null edit.

Bug: 73463
Change-Id: Ic22597dfed11de3823471673404090a9bce12928
On save, if there was no 'last modified' text at the bottom of the page, add it

Just hope that wgMaxCredits is 0.

Change-Id: Idf4a7cceb0650eaec4442244066d875a3ff38e06
Merge "Don't try to get newtimestamp from edit if no change was made"
Merge "On save, if there was no 'last modified' text at the bottom of the page, add it"