Add SQLite3 implementation

This PR adds an improved version of `IBlobCache` based on SQLite3 - using SQLite3 instead of the current implementation has a number of benefits:

* Only one file, easy to ship across to other people
* Insert => immediate GetAsync no longer fails
* Serialization now uses BSON instead of JSON, making it way more compact
* Type information is now stored in the record, meaning that operations involving groups of objects (`InvalidateAllObjects<T>`, `GetAllObjects<T>`) can now be much faster
* Operations now never hold locks (i.e. hold up background threads), they are serialized asynchronously via `KeyedOperationQueue`
* Code is vastly more simple (~200 lines vs ~500 lines)

```
TODO:

[ ] - Merge in the Async Invalidate stuff and implement it in the SQLite backend
[ ] - Honor Serialization settings (IObjectFactory, SerializerSettings)
[X] - Create projects for WP8, WinRT
[X] - Fix Dispose behavior so test passes
[X] - Enable Encryption
```