The window size was restored too early which caused the window to be a little bigger then it should on each launch. Restore window size after that window was mapped.
Play video with external subtiles by:
* selecting and opening both video+subs from file chooser/manager
* dropping subtitles file on player window
* opening subtiles from file chooser/manager while video plays
* send their file path/uri to player via WebSocket message
Window headerbar is hidden at all times. We do not want to execute the logic that comes with GtkHeaderBar, so we simplify it by using GtkBox as a dummy widget.
This avoids D&D controllers clash and allows to freely customize how maximize, minimize and close buttons work (differently for e.g. web application) and where are they placed
The "clapper_src" directory name was unusual. This was done to make it work as a widget for other apps. Now that this functionality got removed it can be named simply "src" as recommended by guidelines.
