morphline protocol buffer command

Most kite users don't need protobuf commands and don't have protoc installed, and the build needs to pass even if protoc isn't installed, including in jenkins and on travis, etc. We can't merge things that require people to install stuff they don't care about. The build needs to pass out-of-the-box.

I propose to ship the generated java classes for the unit test as part of the git repo, plus a mvn flag to regenerate these classes (defaults to no codegen), and have mvn use the shipped classes. This way protoc isn't required for normal usage, and only temporarily required if you were to change the unit test or add more unit tests.