Fix the WriteTest tests.
Fix the WriteTest tests.

The tests were asserting invalid information:

WriteTest.G6_UpdateTableWithStringPK() required a Customer with CustomerID 
'BT___', which doesn't exist.  Insert and remove it for the test.

WriteTest.G14_AutoGeneratedSupplierIdAndCompanyName() needs to have
CompanyName specified, as Northwind specifies that CompanyName is NOT NULL.

WriteTest.G16_CustomerCacheHit() is changed to use .First(), as that's what
the comment says will directly hit the cache (and is apparently what the test
is intending to test).

WriteTest.G17_LocalPropertyUpdate is [Explicit] under L2SQL (mapping issues).

WriteTest.G18_UpdateWithAttach() is ~completely bogus -- L2SQL generates a
NotSupportedException when you take entities created by one DataContext and
Attach() them to a different DataContext instance.

WriteTest.G19_ExistingCustomerCacheHit() needs to refer to a valid CustomerID
(AIRBU doesn't exist), and use the .First() mechanism (as mentioned in
WriteTest.G16_CustomerCacheHit()).


git-svn-id: 1800f71f313d917366f95485fa960eed04b40598@1152 33146b6e-df29-0410-a1ca-39be37fb9416

Sectoid/dblinq,sharique/dbinq,sharique/dbinq,Sectoid/dblinq