* Added old Hyak-based SDK source code.

Hyak-based SDK (Microsoft.Azure.Management.Sql 0.XX.0-prerelease) and
AutoRest-based SDK (Microsoft.Azure.Management.Sql 1.Y.0-preview) cannot
both be referenced in a single assembly because they have the same
assembly name and same namespace. In order to migrate from one to the
other, we are adding Hyak-based SDK source code directly to the PowerShell
repo where it is rebuilt with a different namespace and assembly name,
therefore allowing both SDKs to be referenced.

* Modified legacy SDK csproj for successful build.

In the previous commit I had copied the SqlManagement.csproj from
azure-sdk-for-net. It did not build successfully due to project
imports/references.

In this change, SqlManagement.csproj is modified so that it builds
successfully. The assembly name is changed to
Microsoft.Azure.Management.Sql.Legacy.

I also removed duplicate MSSharedLibKey.snk files from other Sql projects.

* Modified Sql projects to reference LegacySdk

Using project reference instead of nuget reference.

* Add script to find/replace namespace in LegacySdk

LegacySdk (Hyak-based) and latest sdk (AutoRest-based) each have types
that have the same fullname (namespace and type name) as one another). In
order to reference these types without ambiguity, LegacySdk needs to
have a different namespace. This script does a dumb find/replace on this
namespace.

* Ran namespace script.

This changes the namespace from Microsoft.Azure.Management.Sql to
Microsoft.Azure.Management.Sql.Legacy.

This was run on both the legacy sdk itself and the cmdlets that reference
it.

* Fixed ServerUpgrade scenario test.

This test was broken by the previous commit. Separated this change from
the previous so that this manual edit is reviewable.

* Updated cmdlet projects to reference new sdk.

Now that legacy sdk changes are complete, cmdlet projects can reference
the new AutoRest-based sdk without conflict.

* Enable scenario tests to create old and new client

* Update server cmdlets to use new sdk.

There are upcoming changes to server api in new sdk and everything depends
on it, so it's a good first proof of concept candidate for migration.

* Update to Management.Sql v1.2.0-preview

* Added breaking change exception.

The affected types have been renamed but are functionally identical.

* Fixed breaking change log

* Removed comments in SqlManagement.csproj

* Updated LegacySdk assembly version