Add abstract MappedSuperclass Party

OPEN - task 78: Proposed Business modules architecture 
http://github.com/DevOpsDistilled/OpERP/issues/issue/78
Apply Nimbus LAF

OPEN - task 79: Create Party Module 
http://github.com/DevOpsDistilled/OpERP/issues/issue/79
Merge branch 'apply-nimbus-laf-to-invincible' of github.com:TheKojuEffect/OpERP
Remove init() method