Fix [#34300] Slider for list of particle systems (keyed particles) is not doing anything. Navigating a list of more than 5 elements requires keyboard.

Systematically adding some custom id to template_list using default UI_UL_list class, this one is commoly used more than once in an area, yielding collision issues if they do not have a custom id...

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54626 954f8c5b-7b00-dc11-b283-0030488c597c
Minor precision in template_list doc, to always use a custom list_id when using default UI_UL_list class.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54627 954f8c5b-7b00-dc11-b283-0030488c597c