Trigger "pre:compile" before app resources are copied

Closes #ALOY-765
https://jira.appcelerator.org/browse/ALOY-765

Allows for operations on `app` files before they are copied to `Resources`, so this operation doesn't need to be done on both or will only be effective on next compile.
[ALOY-765] add jmk hook prior to copying in assets "pre:load"
Merge pull request #255 from appcelerator/pr/252

[ALOY-765] add jmk hook prior to copying assets/libs "pre:load"