Improve post-build command, fix spelling mistakes.

[korygill]

This is captured as bug #398.

The post-build command gives an error when run multiple time because the directory already exists. A simple IF can fix that. Also, the file appears to have LF and not CRLF in it which causes VS2015 to treat the command as one instead of multiple commands. There are also some spelling mistakes in various files, the worst being in about_PSScriptAnalyzer.help.txt. I have fixes for all the above and will submit a pull request shortly.

[msftclas]

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[raghushantha]

Thanks for the fixes, Kory!