mime: Implement weight-based extension globs.

When matching an extension glob (*.foo) with MimeType.fromName(), the
weights were not being taken into account. This caused extensions
matching multiple MIME types, such as .png (image/png and
image/x-apple-ios-png) to return the last one added to the list.
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