Revert "Extended test cases; python3 support"

This reverts commit 38c19147e9b7f21eda55bf5799e15049f9dd25e5.
Revert "Catch all execptions, vars for exit codes etc."

This reverts commit 901326702202912a17a2fbd47ada0eb3b8003b13.
Constants for return codes
Constant for config section name of commands
Catch regex and escaping exceptions
Test cases for regex + escaping exception handling
Catch exception on command formatting
Test case for formatting exception handling
Test case to check type overwriting of commands
README.md: Note re command definitions
Test cases: python3 compatibility