Distinguish between regular errors and configuration errors

I've now hopefully improved a lot of the HGVS search error messages to be more user friendly.
As such, (just in the Shariant branch for now), I no longer convert errors for nonadmin users to "HGVS Search Failed".

I suggest we make a new kind of Error "ConfigurationError", e.g. in mane.py
`"Need to insert genes/transcripts and HGNC"` would be a ConfigurationError. Basically any error message aimed at admins should be a ConfigurationError.

If search gets a ConfiguationError, it should report it to Rollbar and then tell the user that there was a problem, and to try again later.
All other errors should be passed on to the user.