Add the ability to search for a definition in a specific language

* _ResourceManager: allow resources to be named anything as long as they
  inherit from the base resource class; gave resources proper names.

* Renamed BaseCommand to Command and BaseTask to Task; applied renames
  throughout earwigbot.commands and earwigbot.tasks.

* Data: refactored argument and command parsing to be completely internal.
  Added docstrings to attributes. Applied changes to Frontend.

* IRCConnection: improved such that we accurately detect disconnects with
  server pings; timeout support. Applied changes to Bot.

* Updated documentation and other minor fixes.