Add a very basic concept of a file handle.

This is in the future will allow us to smartly detect when to pass file
handles, or contents of a file.

Change-Id: I2b3cb2164fd3a26a9ed6d53df1e470ed1cb69ee8
Move everything over to the easier to use JobRequirements and JobContent.

Change-Id: I8031fe810880e0a2da970a194a0a0d2b50cd26f5
Merge branch 'easier_reqs'

Change-Id: Iea381b01c0827e6458b1d5aa5441dd7bc460818b