Move cache directories to the data folder

Every time an update is pushed the various cache folders are overwritten
as well. Fix this by moving them to the data directory.
The feed-icons folder is special since it is actually used to
provide the icons. So instead of changing the location of it create a
symbolic link.
Merge pull request #13 from maru-sama/persistent-cache

Move cache directories to the data folder
Merge remote-tracking branch 'disconn3ct/master'