Allow modification of flags on Recent Changes
Moved the message map in ChangesList::flag to a new setting named
$wgRecentChangesFlags and used it keys to iterate over the flags
Also allow setting the class to deal with minor vs. minoredit
Also make ChangesList::recentChangesFlags public to be used from
extensions, when they will build its own line
Changed one list of placeholders to use recentChangesFlags to have the
correct number of spaces there
Change-Id: If69de05c4edec4e84c3e059090b9cb89845e3269