Now assignment->types are installed / upgraded using the upgrade_plugins() standard way. And they are installed in the SAME page than the assignment module itself.
Right now upgrade_plugins() outputs the header of the page, so some warnings are showed because it's printed twice.
Would be a good idea to add one new optional parameter to upgrade_plugins() , call it "embeded = false" to skip header and footer printing?
I think it could be useful for other "submodules" in the future.