Fix Activator homepage folder browser

I was not able to browse to find my existing projects as the gotoParent function was removing the drive letter from the path.

Please review the following changes I made to correct it:
* Replaced backslashes with forward slashes in the initial path (ActivatorProperties.GLOBAL_USER_HOME)
* Added variable windowsEnv and set it based on whether the first character is a slash, i.e. not Windows
* Added functions isRootDir, and getParentDir.
* Updated the gotoParent function to make use of getParentDir