Added client string to configuration

Clients can set their own client string which will be send to connected
peers during the handshake.
Added AddFunds method
Commented out code due to rewrite vm
Comply to Callee structure
Closures and vm based on closures

Status: Work in progress
Fixed issue with stack where it sliced of the wrong values
Moved code around
Comply to Callee interface
Added encoder interface
Some minor updates