feat(task-alias): add 'alias' config

[Merott]

Allow defining task aliases through an alias config. alias is an object, with the key being the name of the alias to define, and the value is either the task name to alias (string), or array of task name strings.

Example:

// warlock.json
"globs": {
   ...
}
"alias": {
   "b": "webapp-build",
   "bc": ["webapp-build", "webapp-compile"]
}

[joshdmiller]

Awesome!

One ultra minor question: should the key be aliases to be consistent with globs, tasks, etc? I can see it both ways: alias is an instruction (hey, you - go alias these), and aliases is a delineation. Do you have any strong feelings either way?

[Merott]

I sort of default to singular terms most of the time, but in this case I don't mind it either way. You're right though, aliases seems more consistent with the rest. I'll go ahead and change that.