Installer: Disable Inno Setup's built-in RestartManager in favor of ours

Our own RestartManager also supports detection of locking processes before
Windows Vista.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Installer: Default to automatically close and restart apps in silent mode

In silent mode, by default agree to close and restart apps that use Vista's
RestartManager API.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>