coverlet.msbuild does not work for projects targeting .NET Framework 4.6

[sharwell]

This regression was introduced in #355.

❗️ This change broke coverlet support for projects targeting .NET Framework prior to 4.6.1. Placing the props/targets in a framework-specific folder makes them dependent on the declared target framework of the project, which we do not want. We only want them to be dependent on the target framework of the currently executing version of MSBuild.

Originally posted by @sharwell in #355 (comment)

[tonerdo]

Hmm..I see. Will update and include in the next release. Thanks

[viceice]

The files can be simply put in the build folder, then it is working fine