Add rulesets

[mariano-aguero]

Closes #73

• Allow to extend rules to solhint through the config file (recommend, default, all)
• See custom config to use (you can create yours) https://www.npmjs.com/package/solhint-config-align-base
• Add ajv schema validator, schema and metadata to rules, and some tests
• Now you can disable a rule with the 'off' flag (eslint style)
• Enjoy it!

Example of .solhintrc.json or .solhint.json:
First install package: npm i solhint-config-align-base
{ "extends": [ "align-base" ], "rules": { "avoid-throw": "off", "indent": ["error", 2] } }
Or you can extend a core rule like all, recommended or default

[coveralls]

Coverage decreased (-66.1%) to 33.076% when pulling 081a910 on feature/add-rulesets into 22b5ca5 on 2.0.

[german-bortoli]

Thanks

So excited to view this PR into the project.

Regards.

[fvictorio]

We'll need to add some documentation on how to create a ruleset.

[fvictorio]

Any reason to reduce from the right? This means that the rules that appear first in the array will override the ones that appear next. I think it makes more sense to do it the other way around, and that's the way eslint does it if I'm not wrong.

[fvictorio]

The rules should have higher priority than the rulesets. Right now, it seems that if a rule is set by a ruleset, then you cannot override it.