[SKIN] SimpleGray

Simple and clean multi resolution skin for OpenPLi or on OpenPLi based enigma2 images.

Skins use automatic scaling, thefore it is available in all, SD, HD and FHD resolutions. Skins use svg images, so their quality does not change at all resolutions.

Will work on OpenPLi images starting from version 8.1 because the older images does not support scaling and svg.

-Improve error reporting
-Fix SyntaxError and disable line too long check
-Change deprecated inspect.getargspec() to inspect.signature() in tests
-Remove screens for deleted modules in OpenPLi
-Fix skin test
-Update actions and dev packages
-Small style corrections in renderer SG_PiconProv
-Fix python3 import path in renderer SG_PiconProv

Thanks Taapat