non-error & failing test for adding InstructionMessage
added InstructionMessage class, got test passing by initialising object
updated readme
added exception class in preparation for validation tests, added invalid msg values
added failing verification test
InstructionQueue class now extends priority queue, refactored tests as neccessary
got invtype test passing, added inv prod code test
inv pc test passing, added inv quant test
inv quant test passing, inv uom test passing
added passing test for time stampt, added comments
Merge branch 'f_add_instruction' into develop, validation and insertion tests passing