On cluster support

Added support for "ON CLUSTER" statement. No clash now with replicated migration option.
Small refactor.
Removed unused code. Removed *.ini file support

Environment variables and CLI

Additional options for configuration:

• via environment variables
• via command line arguments

Setup update

• Fixes and additions to setup.py

Beta release

Initial version of ClickHouse migration tool:

Features:

• Migration files creation
• Possibility to apply changes to replicated and single instances of ClickHouse database
• Tracking applied migrations