Adding parallel and distributed file system interface

This adds in the user facing interface for exposing parallelism in a parallel/distributed file system in a meaningful way to the user. It also adds in the runtime bindings and the plumbing for Lustre and other such parallel and distributed file systems and implements it for the HDFS plugin.

@mppf said he would review.

[Note: This is a revised pull request that fixes whitespace changes]
This findloc is just a utility function for file.locsforregion so should either have a name like chpl_findloc or be an internal method to file.locsforregion.