Redesign the bslint.json file

[TwitchBronBron]

The bslint.json file is a bit basic. I really like the way eslint json files work, and I think that same style would work well with bslint. Here's an example : https://github.com/rokucommunity/brighterscript/blob/master/.eslintrc.js

Here are some of the features I'd like to see:

• the ability to "extend" / inherit a default rule set
• simple way to override a rule's severity, with consistent severity names.
• a consistent structure for all rules. eslint allows a string for severity, or an array where severity is the first entry. Then a custom data structure for each specific rule after that.

This should probably be implemented as part of the v1 rewrite, so the breaking changes land at the same time.