Generate javelin config dynamically

The current javelin config makes assumptions about what services
devstack has actually deployed and will fail if those assumptions
are not correct. We're now testing more than just the default devstack
topology. The list of resources grenade expects javelin to act on needs to
be flexible if we want it to support these non-standard configs. This adds
a tool to dynamically generate the javelin resources yaml depending on
what services devstack has deployed, using the existing resources.yaml
has a base.

Change-Id: Iaf9381e185d4875e6098fe5f3573b5bb61c01e33