Allow modules to override the site logo even if the reference application is running

This wiki page describes how to change the site logo: https://wiki.openmrs.org/x/fAEzAw

However this may not work if there are multiple modules that try to configure this (and the reference application does).

We need to allow a module to override the icon and url even if the referenceapplication module is doing so already.

Dev Notes

Probably the quick fix is to change the code around this line, so that instead of getting the first extension, we get the one with the lowest order property.

https://github.com/openmrs/openmrs-module-appui/blob/724b4a9c8c434bb723b040a2ede8566612db481f/omod/src/main/java/org/openmrs/module/appui/fragment/controller/HeaderFragmentController.java#L39