This patch supports the corner case of users wanting to install app-templates in the scripts path set in their user-preferences (not used by default).
There have been 3x reports about this, while I'm still not so keen to support it, this patch shows how it might be done.
This still seems like adding checks for a corner case, submitted the diff to get other devs opinions.
Some implications for this patch:
- Requires a new module name just to support this directory: bl_app_templates_user_prefs.
- All other paths aren't expected to change at run-time, where as BLENDER_PREF_SCRIPTS can be edited by the user or reset when loading factory preferences.
- Potential order of initialization errors as app-templates may be loaded early in blenders startup.
- Having preferences used in application level paths which aren't expected to change may be error prone.