variable to skip package name checks

[gburanov]

It is a pity that two functionalities are merged together in the rule rule.var-naming - checking variable and package naming.

In our company we find variable naming check very useful, but we do not want to check for packages naming.

Therefore I propose to add option to skip package name checks

[chavacava]

HI @gburanov, thanks for the PR, I've left some comments in the code

[chavacava]

@gburanov Please also:

1. update README.md and RULES_DESCRIPTIONS.md to document the new parameter.
2. Add testcases to check the parameter is working as expected

[gburanov]

@chavacava I made the changes you suggested

[chavacava]

Thanks @gburanov !