Support schema parameter on CreateAppender

[Chris-Barton]

This change is to allow the passing of a schema option on the CreateAppender something supported on the native method but not with the ADO.NET Provider. See issue #94

[Giorgi]

Can you add a test that uses not null schema?

[coveralls]

Pull Request Test Coverage Report for Build 4628965211

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 85.781%

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Totals
Change from base Build 4628037286:	0.01%
Covered Lines:	712
Relevant Lines:	829

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💛 - Coveralls