Add support for remote Windows Update installation

[LordHepipud]

Add support to fetch and install Windows Updates by using Cmdlets.

We should also add a feature allowing the Icinga Web 2 module to install updates remotely, if the following requirements are fulfilled:

• The PowerShell Module is running with sufficient permissions to install updates
• The PowerShell Module has the command for installing updates enabled (disabled by default)
• The Icinga Web 2 users inherits the permission to install updates

Otherwise commands are rejected.

See also https://github.com/LordHepipud/icingaweb2-module-windows/issues/11