Adds support for changing the capitalisation of the @override decorator

[ChiriVulpes]

This code originally supported changing the casing of the JSDoc tag as well, but I don't think anyone would ever want that, I've never seen capitalised JSDoc tags before. With that in mind, this PR only adds support for changing the casing of decorators.

Example usage:

{
    "extends": [
        "tslint-override"
    ],
    "rules": {
        "explicit-override": [ true, "decorator", "@Override" ]
    }
}

Note: This changes the decorator matcher to only work with the decorator of the correct casing. With that in mind, it may be a good idea to add another warning if we see a decorator with the wrong casing, and maybe change those to the correct casing? Should that be an additional option, tho?

Another note: I was going to write some tests for this but I wasn't quite sure how I should do it (especially since I wasn't sure how we want to handle the incorrect casing thing).

[hmil]

The access rights of resources/test.sh have changed for some reason. Try chmod +x resources/test.sh. I'll take a look at the rest later.

[ChiriVulpes]

It doesn't seem to do anything for me (running it via git bash since I'm on windows; if it is doing something, it's not making something I can commit).

This must have happened as part of the upstream merge somehow. I didn't edit the file. I could probably fix this easily by just making a new branch and making a PR from that, should I do that?

[hmil]

Oh man, permission issues on windows. You're in for a ride.

Perhaps you could export a diff from your PR with something like git diff 94d2811 HEAD > ~/tslint-override.patch. Then get a new, clean clone of the repo, cd into it and apply your patch with git apply ~/tslint-override.patch.