Add git & svn support to the audit server

[jeffpaul]

Originally reported by @jeffpaul on 30/Oct/17 4:16 PM:

Audit server currently uses exec() calls for dealing with git. A similar approach can be taken to deal with svn. Ensure that SVN is baked into the audit server docker image.

We will want to think about how important is the ability to specify a branch or tag to checkout. For git it will use the repo default branch.

[valendesigns]

We currently only support zip but can easily add git and svn to the image, the hard part is setting up Go to use those project types.