Improvements for binapi-generator and support VPP 19.04 in statsclient

Improvements for binapi-generator and support VPP 19.04 in statsclient

- RPC service client implementation for dumps requests
  now streams responses
- RPC service generation is now enabled by default
- examples now allow setting binapi socket address
- input dir flag for binapi-generator will recursively look
  into dirs to support core/plugins in /usr/share/vpp/api
- minor improvements in debug logs
- add support for VPP 19.04 for statsclient

Change-Id: I0939ee3aa6e9f850d073fc5c87aff4ccc56b0d70
Signed-off-by: Ondrej Fabry <[email protected]>