Redesigned inline image internals using unique IDs.
Improve on recent inline image changes.

Storing unique ID as key value and using the URL as the actual key so that we only have to query the URL as the key to check for duplicates instead of enumerating throughout the dictionary each time to find duplicates.
Hide inline images by default and request their headers to check for a size limit and actual content type.
I already know someoen will ask for it so making max filesize configurable.
Add native support for *buffextras in ZNC.
Merge pull request #401 from xlexi/master

Added support for Chromium in the /page command.
Select correct tab by default.
Inline image support for dropbox.com.
Inline image support for instacod.es.
Use conditional to allow inline images to only be enabled for specific channels if global state is disabled.
Inline image support for docs.google.com
Save state of the correct button.
Fix typo.
uggggg
Do not spend time creating new instance of NSDateFormatter for each IRCMessage instance.
Keeping this value around seemed too costly in instruments.
Moving to view-based member list step #1
Get rid of this.
Moving to view-based member list step #2

Not complete.
Consider isAway a state requiring redraw.