Related to #1286

(cherry picked from commit 4e62bfb3)

Related to #1315 #1302

don't invalidate when dragging clip in and out of timeline

Related to #1314

When Kdenlive runs inside a sandbox enviroment like with Appimage,
Flatpak or Snap it needs to resolve some paths rekursive. This is
currently detected by whether a custom config file was specified or not.
This patch changes the behaviour. The package type is now detected
through the envvar PACKAGE_TYPE. You can set it to "appimage", "flatpak"
or "snap" to let Kdenlive run in sandbox mode.

Farid Abdelnour authored Jan 23, 2022 and Julius Künzel committed Jan 23, 2022

Should fix bad quality renders in videos with alpha profile.

Fixes #1075 
BUG: 436879
BUG: 430093
BUG: 357153

Farid Abdelnour authored Jan 22, 2022 and Julius Künzel committed Jan 22, 2022

BUG: 448010
CCBUG: 436879
Related to #1075

Timeline preview: when saving, store rendered chunks in a more clever list (like 0-1700 instead of listing each 0,25,50,75,... until 1700).
Will result in much smaller files.
Related to #1266

Shift+0 is ambigous with ) on some keyboards

Related to #1115

Fixes #1309

Related to #1306

Related to #1307