Resolve velocity template errors on webapp startup

Velocity will by default log an error for any requested templates that do not
exist. This changes the code such that a check is done first before requesting
the template. If not found a debug message is generated by fedora rather than an
error message generated by velocity.

[Finishes #54879858]
Merge pull request #106 from nigelgbanks/54879858-velocity-template-errors

Resolve velocity template errors on webapp startup
Updating namespaces to match new ontology with HTTP URIs, using variables instead of literal namespace strings where possible to reduce maintenance issues
Merge pull request #107 from escowles/namespace-reorg

Updating namespaces to match new ontology with HTTP URIs
Update policy-driven-storage for runtime configuration

Move configuration from Spring to the repository
Add REST endpoint for runtime configuration
Resolves:
  https://www.pivotaltracker.com/story/show/49059799
  https://www.pivotaltracker.com/story/show/54197412
Upgrade to Modeshape version 3.4.0

Resolves: https://www.pivotaltracker.com/story/show/55169746