Updated Spanish translation
Updated Spanish translation
Remove mainwindow's fullscreen feature

With all the efforts I put into making it work, it breaks my heart to remove it.
However, with the planned use of client-side window decorations with HeaderBar,
it makes no sense to keep it.

First, the HeaderBar saves a ton of space, making fullscreen much less needed:
it takes 48 pixels instead of the previous 101 pixels.

Second, the way the fullscreen feature worked was by ripping out the
main toolbar, adding it on a temporary floating widget, then doing the reverse
operation when exiting fullscreen. This approach won't work with the HeaderBar,
as you cannot unset the client-side titlebar decoration, and the buttons we put
in HeaderBar are not contained in a GtkToolbar widget (themes don't like it).
Manually ripping out each and every widget from the HeaderBar isn't an option.

Removing this also reduces code complexity and problems (such as dealing with
detachable UI components or multiple monitors).
viewer: Add a button to undock the viewer directly instead of using menu actions
Updated Brazilian Portuguese translation
Updated Polish translation
Updated Czech translation
project: Flush the pipeline when we set restriction caps

This way we make sure that the viewer updates
Updated Lithuanian translation
project: Emit "rendering-settings-changed" when the pixel aspect ratio changes

Otherwise aspect ratio changes would not always get applied.

Fixes bug #721973
mainwindow: Actually use DAR (not PAR) to set the viewer's display aspect ratio

Using the pixel aspect ratio to set the viewer's (display) aspect ratio
made no sense. We had a nice unused method for that exact purpose.

This also happens to fix bug #722003
clipmediaprops: Use proper names for checkbutton widgets
clipmediaprops: Prevent setting an invalid framerate from a misdetected clip

Fixes bug #721888
Add a comment for translators to clarify "Pixel aspect ratio"

Also update the French translation
project: Default to a square pixel aspect ratio

This would be a saner default
Updated Polish translation
Updated Brazilian Portuguese translation
dogtail: Remove testing of missing font chooser element
timeline: Remove previous/next keyframe menu items

The logic is missing and we are not sure how useful they are.
The unittests when the functionality has been added are long gone:
efa26eb0
timeline: Clarify a fixme