Implement Category Cache and ActionsListFile.applicationsForCategory()
actions: Implement ACTION_VIEW and ACTION_EDIT in addition to ACTION_OPEN
actions: Do not duplicate apps in applicationsForMimeType
mime: Fix various issues with MimeType action methods
mime, actions: Unalias directly from inside MimeType instead of xdg.actions
mime: Globally import xdg.actions
Merge branch 'master' into intents
mime, actions: Add an optional action key to associationsForMimeType (and cousins)
desktopfile: Only return an instance of DesktopFile in lookup() if there actually should be one
desktopfile: Use a global DESKTOP_ENTRY variable
desktopfile: Get rid of old duplicated IniFile/ConfigParser logic
desktopfile: Error out if a desktop file is missing the required Desktop Entry section
actions: Implement edit/view actions for ACTIONS_LIST
actions: Rework removedAssociations() logic

We now only return associations that have been removed for *every* given
action.
This also means that, in order to get backwards-compatible behaviour, we
need to pass ACTION_OPEN. If passing ACTION_ALL, the associations are
only considered removed if they have been removed for ACTION_OPEN,
ACTION_VIEW and ACTION_EDIT.
actions: Declare global dicts of actions to make it less verbose to use programmatically
actions: Use an OrderedSet for applicationsForMimeType()
mime: Remove MimeType.associations() (was unused)
actions: Implement Intents Cache