First commit of a what.cd input plugin.

Nothing works except logging in and performing a search
Use PluginError instead of returning None
Changed config validation to use the schema property instead of the validator
Change API parameters without a mapping to a list instead of a dict
Add parsing of response
Fix schema
Made dictionary comprehensions Python 2.6 compatible
Add rate limiting
Fix paging logic
Fixed boolean options not being correctly used
Added support for the 'searchstr' parameter
Fix boolean behaviour
Improve isinstance logic
Fix case issue in params
Change case of input parameters

This change can be stripped out if it would be better to leave them in
title case instead of lowercase (except acronyms and brnd names).
Added documentation
Fix taglist
Added some basic tests
Made the User-Agent configurable
Improve invalid login detection