curly: Allow to filter affected keywords and pass keywords-exceptions

JSCS has rules disallowCurlyBraces and requireCurlyBraces that allows to pass keywords: ["if", "else", "for", "while", "do", "try", "catch", "default"].

More over requireCurlyBraces has allExcept option that works like exception for passed keywords:

    - `'allExcept'`
        - Array of keywords inside of the block that would allow curly braces
        - Ex: ["return" , "continue", "break"]

E.g. for:

"allExcept": ["return", "continue", "break"]

it works like:

// Here we need curlies
if (true) {
  // Dummy
} else {
  // Another one
}

// And here we don't
if (true) return false;
else if (false) break;
else continue;

The current curly options and the first suggestion:

"curly": [2, "all"]
"curly": [2, "multi"]
"curly": [2, "multi-line"]
"curly": [2, "multi-or-nest"]
"curly": [2, "multi", "consistent"]

I suggest to pass an Object with keywords and exceptions as the last parameter:

"curly": [2, { "keywords": ["if", "else"], "except": ["return", "break"] }]
"curly": [2, "multi", { "keywords": … }]
// or even:
"curly": [2, { "schema": "multi", "consistent": true, "keywords": … }]

Related: https://github.com/eslint/eslint/issues/4007

[mysticatea]

Some ESLint’s rules have overrides option: keyword-spacing, space-unary-ops, and operator-linebreak. So, how about the overrides option for consistency?

For example:

{
    "curly": [2, {
        "type": "all",
        "overrides": {
            "if": {"type": "multi"}
        }
    }]
}

[aladdin-add]

I’m willing to implement this.