project configuration values

error handling for missing project configuration values.
Support preselecting unit test classes

Add support for pre-selection of unit test classes when the UI is
generated
default python for freeze_dev_osx.py

Update build script to use default python if it doesn't exist in
build_settings
Update to Compile Project Build

returns just the class compile erorrs.
plugin settings handling

Improved settings loading and parsing, add default return value