Clean up unit tests so they can be used for the Oracle provider and one bug fix.

The tests can now be soft linked to the ServiceStack.OrmLite.Oracle.Tests
project.

Fix the test for null updates in OrmLiteWriteExtensions to allow empty strings
as well as null.
Merge pull request #364 from BruceCowan-AI/CleanUpTests

Clean up unit tests so they can be used for the Oracle provider and one ...