From Ivan: Linking with SDAPI based on Directory.Build.props instead of HAVE_SD definition.

Updates on how to link with SDAPI.

There are two files that are used for building locally that should not be pushed to OSDU. When present they enable fetching the seismic store extensions from a local NuGet repository. Left out the software builds normally but without cloud access. List them in .gitignore to prevent accidental commit when copying files from the local repository.