Add lint groups to Q#

[orpuente-MS]

This PR adds the necessary infrastructure to define lint groups. It also adds the deprecation lint group, which allows the user to enable all deprecation lints at the same time, which are set to allow by default.

A lint group can be added to the qsharp.json manifest as follows:

{
   "lints": [
      { "group": "deprecations", "level": "warn" }
   ]
}

[minestarks]

Should we update our qsharp.json schema? ( vscode\qsharp.schema.json )

[minestarks]

Since level is a common field, I probably would have organized the types like this - fewer structs. It doesn't make a meaningful difference at runtime, and it might make deserialization awkward I don't know. So take it or leave it - I just wanted to make sure you considered it

struct LintConfig {
    kind: LintConfigKind,
    level: LintLevel,
}

enum LintConfigKind {
    Lint(LintKind),
    Group(LintGroup)
}

[minestarks]

Hmm, I just saw unfold_group above - my suggestion would probably make that function more awkward. So I can see why you did it this way

[minestarks]

Please add copyright header