i18n: Passcrow should not just be in English

[BjarniRunar]

Things that need to be translatable:

• Server-generated Verification messages
• passcrow CLI tool user-interface

Things we don't want to translate:

• Low level error messages
• Log messages

What should we do when low level error messages leak into the UI of the CLI tool? Should make the library throw more granular exceptions so consumers can interpret and translate as they prefer?

[BjarniRunar]

There is now a passcrow.messages module which is used to translate the verification messages generated by the server. We're still too alpha to solicit translations, but things are progressing.