Improved few plugins and added new fields to config file for bot

Bot now takes 2 additional params from .cfg file: server and port - it's better to not keep those hard-coded into .py files

bitly plugin uses `bitly_username` and `bitly_api_token` instead of `username` and `api_token` 

xkcd plugin has "search" function e.g. .xkcd 123 will return comic 123 url and title

reddit.py plugin now returns more useful information when link is posted, such as title, selftext if there is any, domain etc.

youtube, xkcd, reddit and duckduckgo plugins now follow PEP8 a bit more although they're still not really examples of good code (especially the reddit plugin)

duckduckgo.py is renamed to ddg.py to avoid any confusion on imports with duckduckgo api wrapper

Config file doesn't contain any information for plugins to avoid old or obsolete data and not to clutter the file - they(plugins) should either recreate that data on first run or users should enter it themselves(documentation for included plugins would be great...)