Added module incoterm #3630

Review ID: 1923002
Merge pull request #1 from param107/feature/task-3630

Added module incoterm #3630
Added default currency
Merge pull request #2 from prakashpp/develop

Added default currency
Added city to incoterm #3630
Merge pull request #3 from prakashpp/develop

Added city to incoterm #3630
Correction in function field method name
Merge pull request #4 from prakashpp/develop

Correction in function field method name
Propagation from sale to invoice #3779

Review ID - 2013006
Merge pull request #5 from param107/feature/task-3779

Propagation from sale to invoice #3779
Move selection options to constants #3854
Release 3.0.1.0dev2
Fix indentation in tryton.cfg
Do not build for python 2.6
Add an empty value for abbrevation
Make year, abbrevation and city required
Add defaults for value and currency
Update README
Release version 3.0.1.0dev3
Bump version to 3.0.1.0