Adds MacAlgorithmProvider.

Some Desktop tests fail.
MacAlgorithmProvider.CreateHash now works on desktop.
Adds support for MacAlgorithmProvider.CreateKey on Desktop.
Adds WinRT-style key derivation APIs.
Fixes build breaks in commonly untested platforms.
Adds CryptographicBuffer.
Divides Crypto static class into NetFx and WinRT halves to make clear which APIs resemble WinRT vs. .NET Framework APIs.
Fixes StyleCop messages.
Fixes build breaks in Release configuration.
Increments version number.
Patched up .nuspec file, hopefully to make the symbols package be accepted.
Improves UI of WP8 tests.
Fixes several tests on Windows Phone.
A bunch more tests pass on Windows Phone.
All tests now pass on WP8.
Fixes a few tests
More tests pass.
35->37 tests pass on Silverlight.
Fixes build warning.
37->39 tests pass on Silverlight.