Fix/exec with quotes

powershell modifications

• The previous way of executing powershell commands had issues with quotes.
• Command execution was changed from directly running a command using java .exec() to writing the command into a script file and then executing that script. The command to execute has to be a single line (probably), and the script then exits with the commands return code. Powershell commands can also throw exceptions which the script catches and returns a non-zero exit code.