Add ContentsTest stub and build infrastructure
Rename wire-format to Vaultaire.ContentsEncoding
Start broker in contents-test
Remove DataRequestMulti from protobuf/
Define contents operation codes
Begin handling contents operations
Add Test suffix to test case source files
Define stub functions for handling operations
Change Operation from enum to full sum type
Disable profiling (for now) to speed up compiles
Restore newtype definition for Origin

Catches errors arising from getting argument order of origin and
payload reversed.