Chaincode-as-a-server: add new 'main' to to start as a server

[mbwhite]

As per the node chaincode, build into the Java libraries the ability to start the chaincode-as-a-service without needing to write additional code. For reference.. node.js chaincode has fabric-chaincode-node server <options> and fabric-chaincde-node start <options>

i.e. a single main that can take an option to start as a server.
see example code at hyperledger/fabric#2990 (comment)