initially added support for NLog 3(.1)

- NuGet-package creation fails due to lack of net20 build (NLog does not
support .Net 2.0)
!!! I do not know how to fix this !!!
- the only downloadable release of NLog is currently 3.0
removed support for .Net2.0
initial merge of pull-request
adding lib reference for NLog3.1
initial add of NLog30 support
adding NLog30 project to .NET 4.0 solution
adding NLog31 projects to .NET 4.0 solution
update errant refs to NLog 3.0 assembly where should be NLog 3.1 assembly
Merge branch 'FroggieFrog-NLog3'