Reorganise Silecs CLI

Reorganised silecs cli structure:

• silecs.py - main script to run
• silecs_const.py - constants
• silecs_env.py - has class SilecsEnvironment which holds e.g. paths to silecs modules which are needed for operations like generate, validate ...
• silecs_utils.py - utils functions used by script

Also Iduring validation, greneration and migration I use silecs version which is taken from silecs design/deploy file (solves issue #66 (closed))