Support for Temp and In Memory DB & added Unit Tests

Hi Stuart, 

Okay there is a lot in here but it is mostly due to the new unit test projects for WPF, Droid, and Touch.  This covers the what I came up with as a result of our discussions in  Issue #7. Feel free to play with it off my ISQLiteConnectionFactoryAdditions branch in my fork before accepting the pull request.  I did add the public domain SQLite3.dll and def file into a folder in the solution. This dll is currently only being used by the WPF Unit Test, and not setup to be distributed with the release code. However there is nothing stopping us from embedding SQLite3.dll within the WPF project itself at a future date to make it work out of the box. 

#### Changes
* Fixed bug in SQLiteNet constructor that prevented Temp databases
* Added to SQLiteConnectionOptions to utilize more for all create operations explicitly or implicitly.
* Added CreateInMemory and CreateTemp to ISQLiteConnectionFactory
* Added CreateEx(SQLiteConnectionOptions) to ISQLiteConnectionFactoryEx which is now the method all other deligate to for creating a connection.
* Added XML comments to all new methods and a few existing and related ones for improved intellisense.
* Added Unit Tests for Wpf, Touch, and Droid for testing all the Create/CreateEx code paths in the connection factory.
* Added the new Xamarin PCL targets to the common library
* Updated WindowsPhone project to target 8.0 due to the new restrictions in Xamarins PCL targets