Implement Playlist functionality. My god...

Too many changes to summarize.

- Fixes #2.
- Fixes #3.
- Fixes #5.
- Fixes #7.

Start work on uncrustify config.

theme/meson.build

@@ -9,7 +9,10 @@ theme = custom_target('Theme generation',
 		'@INPUT@', '@OUTPUT@',
 	],
 	depend_files: files([
+		'components/_cover-art-button.scss',
+		'components/_gtk-overrides.scss',
 		'pages/_music-local.scss',
+		'pages/_playlist-page.scss',
 		'_button.scss',
 		'_disc-view.scss',
 		'_expander.scss',