fix RMCProfile issues on macos

[Kvieta1990]

This PR fixes several issues with running RMCProfile in GSAS-II on MacOS,

• When executing the RMCProfile fitting, two terminal windows would be created and the one with RMCProfile running is hiding exactly behind a terminal without anything running. This behavior is a bit confusing. The PR fixes this by having only one Terminal window while executing RMCProfile.
• Specifically on MacOS, while checking the existence of total scattering data, we have to provide the full path.
• The wildcard for opening file for RMCProfile plotting is not recognizing pattern '*.csv'. On Windows, this works fine but MacOS does not seem to like the wildcard and it will grey out all files, preventing us from selecting any files.