3rd round of modifications to EDMX Model. Added few, removed few.

Further refined Entity model. Removed Regions and Zones and combined
them into a new entity Location. This along with Entity Type Entity will
serve all locations. Also added Corporate Role entity, Role Type and
Employee_Role (many to many from Counterparty) entity. These will serve
multiple functional roles of employees. This along with Business Entity
will also enable assigning a single employee various functional tasks
from various business units. Also added related department entity.
On the Accounting side, added Invoice, Order and order Type entities,
these will serve having both sale and PO in single order table, and both
sale and purchase invoices in one single invoice table. Further added
skeleton accounts and type of accounts tables which needs further work.