[SPARK-7205] Support `.ivy2/local` and `.m2/repositories/` in --packages

In addition, I made a small change that will allow users to import 2 different artifacts with the same name. That change is made in `[organization]_[artifact]-[revision].[ext]`. This used to be only `[artifact].[ext]` which might have caused collisions between artifacts with the same artifactId, but different groupId's.

cc pwendell

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #5755 from brkyvz/local-caches and squashes the following commits:

c47c9c5 [Burak Yavuz] Small fixes to --packages