Add hl7dump.py

[JonathonReinhart]

This script is used to dump out HL7 messages in a verbose format. It is a useful tool for those learning about the HL7 format, as it makes it easy to understand the various fields, along with their names and implicit datatypes.

[coveralls]

Coverage remained the same at 92.554% when pulling 35b2b28b4aa21494519d30322bf8e8ee0720181d on JonathonReinhart:add-hl7dump into 9d40fe57f4c153bdaff5a46a2a2d735578b59f25 on crs4:develop.