The component version must be numeric, but we want to display e.g.
Qt Creator 4.0.0-beta1 in the installer title.
The change adds a -d parameter to the script and adds corresponding
replacement variables.
Display version falls back to component version.

Change-Id: Ia8bcd05444e280f8a44ab321b043f4031725600d
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>