Reducation in target frameworks

[thompson-tomo]

Describe the solution you'd like
The unleash nuget is no longer compiled for net451 & net46 as the net45 can and should be used
The unleash nuget is no longer compiled for net47 & net472 as the net461 can and should be used

The current additional frameworks are adding un-necessary bloat to the package especially as newer dotnet functionality is being implemented.

Describe alternatives you've considered
Removal of support of net 45 to avoid target framework conditional code

Splitting of the package which in hindsight is a preferred option.

[daveleek]

We're planning to overhaul supported/packaged framework versions