* Enable SqlDataRecord TVPs on netstandard1.3.
* Update netstandard2.0 SqlClient references to Preview 2.
* Skip TransactionScope tests for netcoreapp2.0.
- According to https://github.com/dotnet/corefx/issues/12534, ambient transaction enlistment is not included with .net core 2.0.
* Update references in Dapper.StrongName.
* Disable parallel test run to stabilize flaky type handler tests.
* Disable parallel test run by assembly attribute.
* Move Issue461 tests to TypeHandlerTests.
* Group type handler tests in a collection, re-enable parallelization.
- Being part of the same collection, type handler tests will run sequentially. All other tests can run in parallel.
* Move tests relying on query cache & type maps to a separate collection.

This reverts commit e7ad0874.

This adds a netstandard2.0 build to Dapper (and StrongName until v2),
adds a netstandard2.0 test lineup, restores most functionality (except
UDTs for SQL, e.g. .UdtTypeName isn't in netstandard2), and also breaks
things not actually implemented or implemented correctly in
netstandard2.0. Pushing this up so we can work through these with the
.NET teams.

Several things are still broken here (and fail tests):
- Parameter decimal values (not filed yet)
- DataTables as parameters
(https://github.com/dotnet/corefx/issues/19708)
- .GetSchemaTable() (not yet filed, implementation is completely missing
from SqlDataReader in CoreFX)

While the compile is clean, the above are runtime issues.
`SqlParameter.UdtTypeName` is a separate issue, that one just wasn't in
`netstandard2.0` at all...so we can't support UDTs there until it is.
See https://github.com/dotnet/corefx/issues/17126 for details.

Due to the way VS test works (by injecting an executable entry point), the performance tests needed to be factored out. I also organized all of our existing tests better along the way.
Actual code changes to Dapper itself are very minor, only formatting and documentation fixes (which we need many more of).

The build.ps1 script is upated to work, but note that <frameworkAssemblies> is not working in .nuspec inside the packages in the new .csproj system. I consider this to be a blocker. Issue is here: https://github.com/NuGet/Home/issues/4853

Add InListStringSplitCount; when set, causes `in @foo` parameters to be implemented using string_split

Related issue: #520

This eliminates the dual solutions and brings Contrib into the
project.json fold.
- Tests are ported to xUnit though SQLite is disabled on DNX due to
Issue #375 (Interop loads fail in the VS runner and  params are busted
regardless).
- Projects are consolidated down to what's currently possible with
project.json.
- Contrib moved to: Dapper.Contrib and Dapper.Tests.Contrib (so tests
appear at the end, no other reason vs. Dapper.Contrib.Tests)
- EF moved to: Dapper.EntityFramework(.StrongName)
- Rainbow moved to: Dapper.Rainbow
- SqlBuilder moved to: Dapper.SqlBuilder
- Packages are removed since it's not current-tooling friendly to keep
them (nor was it using them).
- xUnit implemented in Contrib via abstracts - this allow us to very
quickly add any database provider to the rig in a very concise way.
- Contrib unit tests fixed in various places - they were not
parallel-runner friendly
- Nuspecs removed, since they aren't used anymore (to eliminate
confusion)
- Removed speed tests for libraries that aren't on current versions of
.Net (what would we be comparing?)
- Perf tests moved to Dapper.Tests (consolidation from
Dapper.DNX.Tests), but aren't activated yet (no define)

This allows full testing from both solutions, all green.

This includes nuget updates for the test libraries but explicitly
excludes the npgsql upgrade, since there are known 2.0 vs. 3.0 driver
issues. If we can assume everyone is able to upgrade - then we should
switch testing over. Alternatively, we need to test both. My preference
would be the former.

Update to rc1 (23516 dependencies); implement test skipping (including case-sensntivity check); swap all explicit #if to vague #if so we can iterate without bulk changes

This let's us run the tests much faster and all from Visual Studio,
command line, and Appveyor.

TODO: Flag missing test methods