BuildArch and mandatory fields added(fix #36)(fix #38)
Implemented logging setup

Fixes #19
Fixed project building
logging: printing output also on screen
added logging to critical methods of components
(fix #37) + more pretty look for import page
Subpackages page UI works (moving files to sub-package)
Small red stars near labels, no highlighting for req. fields
Two buttons for import (fix #40)
Import text field changes during writing (fix #41)
More pretty highlighting of import
Subpackages page - removed tree children problem
Uncommented base classes methods
gitignore: added rpg.log
base: implemented compute_checksum method
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Base: add setup_workspace method (fix #44)
base: renamed paths + using pathlib.Path everywhere
logging: moved into Base class
plugin_engine: renamed plugin phases (fix #29)