This function is supposed to deprecate current `rgba_from_argb` function.
Other changes:
* fix some debug messages using print instead of logging.debug
* add datadir as a constant
This commit is the first in a series of commits that will introduce new CLI interface for Gradience. Currently we need to move some parts of code that reside mostly in frontend modules to their new backend modules, and this commit is the beggining of this whole ordeal.
* Refactor Preset model object, in order to make it more readable and to allow `new` function that directly takes new values for properties
* Move presets_dir from models/preset to new backend/globals module
* Create new utils/colors module (will be used in later commits)
* Update all modules that are affected by above changes
