Honor a --no-gpg-options flag (and setting)

For those with intractible options files
Various bugfixes and improvements

* We weren't hitting the cache on fingerprint_to_username lookups due to case incompatibilities.  Solve this with a sledgehammer; always convert lookups to lowercase.
* Close keybase/keybase-issues#278 -- a broken error case that would have crashed anyways
* More debug messages
* More fixes for people who specify `primary-kerying` or `keyring` in the gpg.conf files.  Disable a few checks for them, and also pass --no-gpp-options through to gpg-wrapper
Fix comments and debugging
CHANGEs