QS in batch mode should send all requests with bot=1

[jaroslaw Tuszynski]

As discussed in

• https://phabricator.wikimedia.org/T247433
• https://phabricator.wikimedia.org/T246746
• https://github.com/magnusmanske/quickstatements_rs/issues/2

bots using QS asynchronous “batch mode” currently flood users' watchlists. The engine should set bot=1 in all write requests, unconditionally. If the user isn't bot, the edits will be saved without the flag and no warning will be triggered.