RecentChanges, RecentChangesLinked, Watchlist: message when no items

Use consistent message in RecentChanges, RecentChangesLinked, and
Watchlist when there are no items to be shown.

Previously RecentChanges just showed empty space and
RecentChangesLinked and Watchlist used two different messages.
Harmonized both the text and the code.

Message added: 'recentchanges-noresult'
Messages removed: 'recentchangeslinked-noresult', 'watchnochange'

Change-Id: Idf9f7a8422d9ad13dc46c69ee284b04cbbe211b7
Merge "RecentChanges, RecentChangesLinked, Watchlist: message when no items"