- First RPC steps

- Work on some flaws in RPC model

- Remove unused TLS settings from Engine and Swarm options

- Add code to correctly encode data over the network

- Add client driver for RPC

- Rename server driver file

- Start to make marshal make sense

- Fix silly RPC method args and add client

- Fix some issues with RPC calls, and marshaling

- Simplify plugin main.go

- Move towards 100% plugin in CLI

- Ensure that plugin servers are cleaned up properly

- Make flag parsing for driver flags work properly

Includes some work carried from @dmp42 updating the build process and
tests to use the new method.

Signed-off-by: Nathan LeClaire <nathan.leclaire@gmail.com>