Removed redundant dependencies in PCL projects
Removed some compilation warnings
Minor code cleanup
Do not use MSBuild engine for Mac (library) projects - seems there is problems to find MonoMac packages
Changed TargetFrameworkVersion to 4.5 for Samples executables to be synchronised with PCL 158 libraries (implies manual editing of project files)
Removed ApiExamples.Touch from 'Debug' configuration mappings in MvvmCross_Mac solution - so that the solution can be builded without errors for Cocoa/Mac