Add Customer, Product, RegionContext, Supplier and Tax Persistence services. Change Buisness to Business
Change PTBuisness to PTBusiness
Add update method
Update README.md
Merge develop-Persistence
Change PTInvoice reference in CreditNote Builder to UID instead of direct reference
Start concurrency tests. Add constraints to GenericInvoice
Start concurrency tests. Add constraints to GenericInvoice
Remove openJDK7 from travis
Start test fix
Merge branch 'concurrency-fix' of github.com:premium-minds/billy into concurrency-fix

Conflicts:
	billy-portugal/src/test/java/com/premiumminds/billy/portugal/test/services/documents/TestConcurrentIssuing.java
	billy-portugal/src/test/java/com/premiumminds/billy/portugal/test/services/documents/TestDocumentIssuingService.java
	billy-portugal/src/test/java/com/premiumminds/billy/portugal/test/services/jpa/TestJPAPTBusiness.java
	billy-portugal/src/test/java/com/premiumminds/billy/portugal/test/util/ConcurrentTestUtil.java
Fix headers
Update concurrency test. Fix test structure.
Merge branch 'concurrency-fix' into develop
Fix getLastInvoice query
Merge branch 'test-fix' into develop
Fix billy-gin dependencies
Merge branch 'develop' of github.com:premium-minds/billy into develop
Update javadocs
Update with locking in issuing service. Update code configurations