Refactor Transmission header into a more pythonic way
Refactor Transmission trailer
Refactor Group Header
Refactor Group Trailer
Refactor Agreement record
Add new exception types

Refactor Agreement record
Refactor Registration record
Refactor Terriroty record
Refactor InterestedParty record
Refactor multiple records:
 - Non roman agreement party name
 - Non roman publisher name
 - Non roman writer name
 - Publisher control
 - Publisher territory
 - Writer control
 - Writer territory
Close #48