Separation project for the NET and GamerServices namespaces
All .NET and .GamerServices files and references moved to new .NET libraries for all platforms

Fully tested on all platforms
Issues logged for code comments:
* #2510 Android platform calls Net.Session.Exit in AndroidGamePlatform.cs
* #2511 OpenTKGamePlatform has been updated and calls Net.Session.Exit
* #2512 iOS platform calls Guide.Initialise in iOSGamePlatform.cs
* #2513 PSM platform calls Net.Session.Exit in PSSGamePlatform.cs

.gitignore updated to ignore the new .NET .csproj files
GUID generated for new projects
Updated .gitignore to something more generic as requested
Update Mac platform, logged another issue:
#2515 MacOS platform Uses GamerServices in MacGamePlatform.cs
Fixed referencing issue for MacOS platform n the FrameworkDefinitions.NET
Replaced iOS.NET GUID
Excluded Web from .NET lib
Removed Lidgren as a dependency for the pipeline builds since it is no longer part of the main platform
Replaced whole inclusions with platform specific exclusions
Retry to exclude web platform from .NET solution
1st pass removing Lidgren from the build installer templates
Updated AssemblyInfo.cs to list each MG library by platform for easier discovery in the GAC
Reverted changes to AssemblyInfo.cs, build issues with assembly versioning will need fixing in another PR

Ready for merge
Reverted too far, adding back the "AllowInternals" for the .NET dll

Ready for merge (once successfully built)
Fixed MeasureString bug

Fixed MeasureString bug related to firstGlyphOfLine. The initial
offset.X was erroneously always set to 0 in an attempt to make sure
negative values didn't allow lines to start less than 0.
gave default variant to session start to prevent invalid pointer error.
Removing duplicate "building font" message.
Remove Flags from SetDataOptions
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Prevent referencing non-existent bones.
MonoGame.Framework GUIDs reverted to previous state with the exception of:

Angle, new GUID generated as it was using the same as the Windows platform
WindowsPhone, new GUID generated as it was using the same as the Windows platform

Fix requested as part of #2560