Slightly overhaul SetAliases

SetAliases was acting weird in case it was told to do
more than just set, add or remove at once (while only
add and remove together make sense and are valid after
this change). This furthermore fixes an edit summary
bug.

Bug: 46743
Change-Id: Ic265625ed4987d4b7eed294ee8df303972834aa0
Merge "Slightly overhaul SetAliases"