...and don't try to connect to the nodes we're already connected to.
Before this change we had a problem of discoverer throwing away good valid
addresses just because they are already known which lead to pool draining over
time (as address reuse was basically forbidden and getaddr may not get enough
new nodes).
* Adds basic RPC supporting files
* Adds interrupt handling and error chan
* Add getblock RPC method
* Update request structure
* Update names of nodes
* Allow bad addresses to be registered in discovery externally
* Small tidy up
* Few tweaks
* Check if error is close error in tcp transport
* Fix tests
* Fix priv port
* Small tweak to param name
* Comment fix
* Remove version from server
* Moves submitblock to TODO block
* Remove old field
* Bumps version and fix hex issues
* block partial persist
* replaced refactored files with old one.
* removed gokit/log from deps
* Tweaks to not overburden remote nodes with getheaders/getblocks
* Changed Transporter interface to not take the server as argument due to a cause of race warning from the compiler
* started server test suite
* more test + return errors from message handlers
* removed --race from build
* Little improvements.
