[module] Added Decorator 'require-privmsg' to allow commands to be specified as only available via PM (Private Message)

Signed-off-by: Eldon McGuinness <eldon.mcguinness@gmail.com>
Merge pull request #390 from EldonMcGuinness/add-require_privmsg-decorator

[bot][module] Added Decorator 'require-privmsg' to allow commands to be specified as only available via PM (Private Message)
[module] Fix hiding of attributes when wrapping a function.

Fixes #390.
[adminchannel] Commands now work via PM and comments are a bit more explicative.

Rewrite of Adminchannel to combine similar code-sets:
  - (de)op/(de)voice
  - (un)ban/(un)quiet

Made all functions available via PM
Revamped comments to be more explicative
Most commands are more flexable as to nick/channel argument order

Signed-off-by: Eldon McGuinness <eldon.mcguinness@gmail.com>