and load this gadget in the launcher

Since e1ab9098 of generic, some functions defined in rjs_gadget_erp5_global.js
were added to gadget_global.js in portal_skins.

However, this caused problem, since users might obtain cached version of file in portal_skins.
Even though we changed gadget_global.js to use must-revalidate HTTP cache,
users may still have old version and not request a new one.

So this commit:
- Re-adds functions to rjs_gadget_erp5_global.js
- Loads rjs_gadget_erp5_global.js at the site launcher, so functions are always there
even if not found in gadget_global.js version

Mark as [NOT FOR GENERIC] since it is a patch to ensure we do not upgrade issues.
I do not know though if this may impact other projects and what the solution would be