Merge pull request #239 from ovatsus/master

Fix handling of optional elements in XmlProvider when using multiple samples
Merge pull request #240 from ovatsus/master

Fixes for portable libraries
Merge pull request #241 from ovatsus/master

Update project structure + use ReleaseNoteHelpers + use FSharpFormating 2.x (WIP)
Update RELEASE_NOTES.md
Drop support for Windows Phone 7