Added new portable target PLLITE for net40+sl+8

Added a new target platform PLLITE to create a portable library which
can be used to target more platforms than the current portable build.

Author:    danneesset <daniel.svensson@hotmail.se>
Make it compile for WP7 again

TypeForwardedTo is not availible on WP7
Add example to demonstrate portable library usage
Package Microsoft.Bcl packages
Update build to target net40+sl5+win8+wp8

Add wp8 as supported plaform for PLLITE
Merge branch 'master' of https://git01.codeplex.com/forks/danneesset/portablesl into develop
Remove obsolete configurations from Rx.sln
Update test projects in the Rx.NET\Test subdirectory
Set up nuget package restore for Rx.sln
Update reference paths in the portable library sample project.
Merge changes from branch 'develop' -- add new portable library target PLLITE and sample project Portable that targets net40-based portable platforms.