Use toast notification to announce new update on modern Windows
versions.
The advantage of toasts is that they look more natural and they are
persistent. So one can find the information about new update in action
center even after notification timed out.
* Fix naming inconsistencies
'Menu' vs 'StartMenu'
* Installer: Remove Facebook link
* Installer: Remove PayPal donate remnants
* OpenShellReadme: Remove info about product version