Perform Build as Task (among other minor updates)

[emanspeaks]

Proposed behavior changes

The following changes are proposed:

• Perform build in an integrated terminal
• Provide more robust checking of Windows paths stored in environment variables
• Allow skipping the definition of kit environment when doing Visual Studio builds
• Load CMake Cache as text file (previewHtml is deprecated anyways)
• Remove hard-coded flags for Visual Studio builds

The purpose of this change

While attempting to build a project with Visual Studio 2017, I encountered issues caused by the presence of the hard-coded flags. Since the user can add buildArgs in the settings, these flags should be manually added by the user, or set as the default value of buildArgs. Once I removed the flags, the build at least started, but encountered errors with using Intel compilers in Visual Studio. Suspecting environment problems, I added the capability to ignore the VS environment. I was still unable to verify the cause of the issue, but noticed that if I copy and pasted the command generated by CMake Tools into an integrated terminal, the build would run successfully. I subsequently changed the build command to provide a command string for a task. I also wanted to add custom configureSettings that are loaded from environment variables, so I needed to enhance this capability to eliminate a number of errors.

[emanspeaks]

This should be ready to merge after someone reviews it...just waiting on a review.

[no-realm]

I am going to merge this for now.