Bug 64833-Add page.userNameHuman as lastNonBotUser

Site.isBot(): return True is username is a bot user on Site.
Site.botusers(): returns an iterator to a dict containing users info.
Page.lastNonBotUser(): returns the last human editor on the page.

Change-Id: I42c8e249072e7d2940f690a0c0ecb8ba2578677a
Merge "Bug 64833-Add page.userNameHuman as lastNonBotUser"