Significantly improve limits (trial 2)

[elifoster]

• Set the default limit in initialization of Butt, with the option to set it later, as it is an accessor.
• Modify most (there are a few with different limits than the typical 500, 5000) query lists to default their limit parameter to this new instance attribute.
• get_recent_revisions and get_prefix_search now properly set their limit parameter with the proper prefix.
• get_full_watchlist now actually uses its limit parameter.
• Improve method declaration line lengths.

See #28

@xbony2