change tree hover icon
preselect All if no category is set, and prevent setting a parent category to itself
preselect default category when subscribing
icons for meta categories
changed settings dropdown
fix category removal
refresh category tree when a category is removed
set parent category of children categories to null when removing a category (fix #38)
don't touch the toolbar when searching
twitter link on welcome page
smarter subscription dialog
format date differently if date is today