Android library now uses native crypto APIs for hash and RSA.
Keyed hash (HMAC) and symmetric encryption still uses mono managed implementation.

4 tests now fail on Android.
Split out some signature verifications into their own tests.
Merge branch 'master' into NativeCrypto
Reduced some switch statement duplication.
Merge branch 'master' into NativeCrypto
Fixes a couple TODO comments.
Centralizes more switch statements.
Merge branch 'master' into NativeCrypto
Android now uses its native MAC algorithm instead of mono managed implementation.
Fixes StyleCop warnings.
Fixes StyleCop warnings.
Moves switch statements.
Merge branch 'master' into NativeCrypto
Android switched to native symmetric encryption APIs.
Fixes invalid input unit test.
Fixes the (still temporary) public exponent assigned when deserializing public keys.
Removes redundant verification from unit test that is supposed to only be made in another, dedicated unit test.
Merge branch 'master' into NativeCrypto
Adds a couple more signing tests.
Merge branch 'master' into NativeCrypto