Add api action to reset reports menu

Giant Rabbit wrote a nice function to convert the report menu such that it files all report instances under the relevant top level category in the CiviReport navigation menu.

In the Giant Rabbit code there are edits to civicrm_navigated.mysql & also the relevant tpl and a page is added which processes the update. There is also (go the rabbit!) unit tests.

However, there is a problem - the civicrm_generated.mysql changes are staler than a stale thing and it's just nasty trying to refresh that because the report needs the navigation id & the navigation id needs the report id.

So, I think I will get the conversion function going as an api (being all new code it should be possible to add into a stable point version) and leave the option of running that api straight after an initial install / via some page or other for someone to address later