Support password-protected keystores for DCP deployments

[ccmcintyre-kingsds]

Bifrost DCP deployments via the Pythonic Compute API were not developed with password-locked keystores in mind; the only regularly tested use case involves passwordless keystores, with the default expected names, in the default expected file system locations (~/.dcp/default.keystore, ~/.dcp/id.keystore). Deployments will stall when attempting to query for a keystore password, as they are not at present exposing a means by which the user can actually respond to that query.

"A monkey patch on wallet.passphrasePrompt that talks this same protocol would do the trick, assuming the protocol is an async event driven kinda thing. Then the Python user could be prompted for their credentials with Python-native UI/UX........similar solution will be needed when the time comes to add oauth integration so that BiFrost users can hit the DCP portal wallet and ditch disk-based keystores." - @wesgarland