Added a system to load news from MultiMC.org's RSS

Currently it doesn't show it anywhere in the UI. That's next.
Merge branch 'develop' of github.com:MultiMC/MultiMC5 into feature_news

Conflicts:
	CMakeLists.txt
Make .ico files usable (the plugin is already included)
Merge pull request #32 from 02JanDal/feature_ico_icons

Make .ico files usable (the plugin is already included)
Add news checking system and news toolbar
Merge branch 'develop' of github.com:MultiMC/MultiMC5 into feature_news

Conflicts:
	CMakeLists.txt
	gui/MainWindow.h
Don't show extra space in status bar, tweak "none selected" message
Merge branch 'develop' of github.com:MultiMC/MultiMC5 into develop
Implement the news button

Make the news button open the latest news post in the user's web
browser.

Also remove the webkit dependency. I was planning on using it to
display the news in a custom window, but we'll just use the user's
browser for now.
Merge branch 'develop' of github.com:MultiMC/MultiMC5 into feature_news
Tweak "More..." to "More news..."
Clean out old assets stuff, fix button hitbox regression
Force cached updater binary to always resolve as stale
Log version, work paths
DEBUG: Add some logging for instance loading.
Notifications system. Mainly to be used in case the updater breaks.
Fix for pre-Qt5.2
Don't try to check for notifications if we don't have a URL for it
Add the option to disable a certain message
Explicitly set the close button to be the default button