better handling of partners in x12 (edifact)

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In x12 edi-partner ID's are more elaborate than in edifact. 
(in edifact often a GLN is used - simple and unique)
X12 has:
- ISA ID
- ISA qualifier: indicate the type of ISA ID: GLN, DUNS, phone number etc.
- GS ID
Most of the time the ISA ID == GS ID.
To make the ISA ID unique, the ISA qualifier is needed.
But to is possible that same ISA ID/ISA qualifier has more GS ID 9more internal 
partners in same holding.
There are 2 ways to handle this correctly:
1. partnerID is a combination of ISA ID/qualifier/GS ID. Can be picked up from 
incoming X12; extract these values in enveloping.
2. Use internal partnerID. Convert this from/to ISAID/qual/GSID.

Original issue reported on code.google.com by [email protected] on 17 Apr 2015 at 4:13