Add build process for Hue

[johnsca]

We want to make this charm more generic, to handle the build of any of our big data resources. I think that Hue is a reasonable second, since its charm is being worked on.

We will need to change the name of this charm layer to be more generic.

[andrewdmcleod]

Hue also needs livy built (for spark):

https://github.com/cloudera/hue/tree/master/apps/spark/java

This requires spark to be installed to build.. and have spark home set. I wonder if this should be a subordinate charm - it could attach to spark to get the libs and env vars and then build that way... just a thought. Similarly the build process for oozie requires pig libs so if it was a subordinate to the pig charm it would be much easier. Of course it could get env's over a relation if it was a principal but what about the libs?