Maximise Components

Add components for showing a piece of media maximised in the application window to components.

This initial commit includes:

• AbstractMaximiseComponent.qml: the base commponent defining the popup
• AlbumMaximiseComponent.qml: show a list of maximised images and videos
• Delegates for an image or a video to add to the album component.
• Basic item to create models for the album / define the spec for a custom model

This is based upon the Neochat fullscreenimage.qml but made generic.

• The buttons are generated from an actions list (empty for the abstract component)
• Has a title with optional subtitle
• Has a leader component (use to show the user info and date in neochat)
• A footer that is the caption for the album component but generic for the base.

Implemented in neochat in network/neochat!824 (merged)

Implemented in discover in plasma/discover!502

TODO

• Video
• Video controls
• Fix blur (currently blows up in neochat when a drawer is open, also not generic) or change for just darker model background (This is looking pretty difficult so deferring to a later mr)
• Only action appropriate to each delegate
• Cleanup

network/neochat#571 (closed)