Multi-Currency

Added support for multi-currency orgs and auto-conversion for currency
type destination fields
Changed test cases to support a more commonly available account field,
NumberOfEmployees

All tests passing, no test skipping.
Code Coverage	96% (109/113)
Great tip @afawcett !

Thanks @aheber for contribution, we are trying to avoid dependency on any CRM object in core LREngine class. In testcase we had no choice, so we used Opportunity object, and imagined user will write own test cases by replacing Opportunity if needed. 

Please incorporate this change, we should be good to go then.