Major changes to fix bugs and refactor code

This includes migrating the .sln file to VS 2012 format, restructuring
Project file layout, restructuring main code into easier-to-read files.

Code changes to fix bugs include:

SADD and related Bulk Reply commands were not working properly. SADD was
adding the length of the argument to the cache instead of the actual
argument itself. These types of commands were changed to follow the
protocol mentioned here:
https://redis-docs.readthedocs.org/en/latest/ProtocolSpecification.html

Also, a UnitTests project was added. While retaining the old tests
(LegacyTests.cs), this will allow for future tests to be added in their
individual units to allow for more granular test results.
Adding .gitignore file