Simplifies WebApplicationException class
Build produces Git SHA 1 and branch name metadata

Incorporated into
* manifests as Implementation-SHA-1 and Implementation-Branch
* REST API at /v1/server/version.
* jsgui (only sha-1) as comment in index.html
Support for adding YAML defined policies to the catalog.

OSGi support included.
Unify entity and policy detail views.
This closes #124
This closes #129
BasicLocationRegistry uses catalogue's root classloader

Means LocationResolvers are loaded from things in the catalogue
This closes #132