fixes #7, remove net4.0, refactor

[trackd]

• fixes ConvertFrom-Html parses special characters as question marks #7
• remove net4.0 powershell lifecycle this appears to be only 2012R2 and older? i think the new() syntax i added last release already breaks on those versions..
• simplified .dll loading to use the .psd1 as it's only loading netstandard2.0
• cleanup of unused code in the .psm1

all tests pass fine on 5.1, 7.4.3, 7.5.0-preview3

adding a parameter that can take the WebResponse object directly fixes the issue so it doesn't get stringified by the [String]$Content parameter

i added a test for that specific issue but relying on that website not changing is not great..

i did try and create a mocked WebResponseObject but couldn't get it to work properly..
might play around with it some more later.