Split project into Core (suitable for all platforms) and platform specific projects

Updated split solution to separate "Core" files from project files
Created separate solutions for all platforms based on latest commits using new "Core" PCL project (tested in Xamarin Studio and VS)

Created two singular projects
 - VS project with all VS supported projects (based on Xamarin FREE install)
 - Xamarin project for all Xamarin Free supported projects.

Tested and built all projects with sample solutions to resolve any split project issues (only known issue was with type resolution in content loading - resolved)

Will work on updating "Portable" solution post update