If the user is in the bot group, mark the edits as bot

This adds the optional &bot=1 flag to edits made by the bot,
if the bot is not in the "bot" group it will silently be ignored.

Bug: 41637
Change-Id: I0fbe0646a7e611202cea921d422ba14598988045
Merge "If the user is in the bot group, mark the edits as bot"