Added support for SQL 2016 (Fixes #26)

[Sagnad]

This change adds support for 2016 as a SQL Server version number and maps it to major version 130 in the get SQL Server major version functions. The value 2016 was added to the schema MOFs for xDatabase and xDBPackage. The unit tests for xDatabase have been moved to Tests\Unit\ as per the DSC Resource Testing Guidelines.

This is to resolve issue #26 where @kwirkykat asked for help.

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This change is 

[Sagnad]

Is there an issue with the fix? We're going to have to use an internal fixed module which is an overhead I'd like to avoid.

[AmarettoSlim]

What's the deal here, is this getting accepted? It's passed all checks and has no conflicts ... it'd be nice to have this merged.

At this point the resource already needs SQL Server 2017 support :)

[johlju]

Wouldn't it be better to change the parameter $SqlServerVersion to be a string value (without a validate set) that takes a string, and that could be 120,130,135,136,140 and then a change wouldn't be require for each version of new SQL Server.
Althought it would be a breaking change, and not quite as good.

[johlju]

@kwirkykat this looks good to me. Can fly over this and merge whenever you have time?

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Reviewed 5 of 8 files at r1, 2 of 2 files at r2, 1 of 1 files at r3.
Review status: all files reviewed at latest revision, all discussions resolved.

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