No remote queries option

[ahwagner]

Some users of CIViCpy may be interested in using it to do secure annotation of variants. We should consider adding an ENV flag that prevents CIViCpy from contacting CIViC for anything other than full-db cache building. While this is typical behavior anyway, such a flag would enforce this expectation, throwing an error if someone tries to do variant queries from an instance without a cache.

This is a small QoL feature that would be nice-to-have and (I expect) simple to implement.

[ahwagner]

Also consider queries made to other services, e.g. Allele Registry for hg38 searches