Porkchat par fredley

Various improvements to Stack Exchange chat. All features are optional, and can be disabled individually. Includes:

* Dark theme - a light-on-dark theme with optional fixed-width font
* Quick-text button - quickly add snippets of text from a menu
* Drag and Drop uploading - drag and drop images onto the chat window to upload them
* Sidebar section collapsing - allow more room for the star list by hiding users/room info
* Room topic change notifier - get a diff message when the room topic is changed
* Image onebox hider - Fade out images and YouTube previews to 0.1 opacity until they are moused over
* Rebecca Black link checker - highlight potential links to 'Friday' by Rebecca Black
* Message burning - hide messages with a burning animation
* mod whois autocomplete, edit deleted messages, give users write permissions from within a room.