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