Add deleteState, addReceiptData, and addEvent methods

[scealiontach]

• Enabled checkstyle for transaction-processor module
• style: some whitespace corrected, and imports ordering corrected
• Added deleteState, addReceiptData, and addEvent methods and implementation as requested in https://jira.hyperledger.org/browse/STL-1175

[scealiontach]

This is great closing up this functionality gap on the java SDK. Could you please add corresponding unit tests the new methods? Unfortunately the existing TP SDK methods lack these unit tests but the signing SDK has unit tests you could look at.

Right thing to do here is to unit test the ZmqContext class since it is the major substantive concrete class. https://jira.hyperledger.org/browse/STL-1172 discusses this a tad. I'll have a look at mocking up the ZMQ stream in order to do it right.

[scealiontach]

@dcmiddle took a pretty good swipe at adding unit test to the Context class. Let me know what you think.