bin: new command jrun
bin: new command jrun

jrun compiles and runs one-off Java classes that use the Chain
SDK. The Chain SDK jarfile must have already been compiled at the
standard location, $CHAIN/sdk/java/target.

To compile the Java SDK:

$ cd $CHAIN/sdk/java
$ mvn package

Closes chain/chainprv#2224

chain/chain,chain/chain,chain/chain,chain/chain,chain/chain,chain/chain