[ALOY-857] Alloy: Add ability to have custom parsers

I am working on a project with a few custom modules, it would be great to be able to add my own node parsers. I can get around that issue by either manually adding my own parser to the Alloy lib but i'd prefer to have them locally in my project directory. Possibly something like: /plugins/ti.alloy/parsers/MyNamespace.MyProxy.js. This could also work as JMK task hook, have the compiler look at the result of say: pre:parser and that could be a list of local parsers. This would greatly increase the flexibility of the compiler, and give us the ability to extend what we can do with alloy as a whole.