Windows Phone 7 csproj

Added a Windows Phone 7 project and linked files from phone 8 project.
Added packages.config for Microsoft.Bcl.Async.
Nuget Package Restore should be enabled to restore the referred
packages.
https://docs.nuget.org/docs/reference/package-restore
Merge branch 'master' into develop
Merge branch 'WP7' of git://github.com/rahulpnath/jet-image-loader into pull-request-30
[project] .gitignore now ignores packages folder, NuGet packages restoring enabled
Merge branch 'pull-request-30' into develop
[release] v0.8.6 dll added! WP7 experimental support!
Merge branch 'develop'