Show fieldset descriptions in modules, menus, plugins parameters

[Bakual]

Issue

Fieldset descriptions don't show up. This is because the code is currently in the layout joomla.edit.fieldset but we don't have this description information there. It looks for a property of the (assumed) object $fieldSet while in fact $fieldSet is an array of fields.
This is the case everywhere except for the component parameters itself. So in modules, plugins, menus and templates parameters and maybe also other places.

Solution

Moving the code to the joomla.edit.params layout where this information (the object) is present.

Testing Instructions

Try to add a description to a fieldset. For example in modules/mod_articles_news/mod_articles_news.xml change

<fieldset
    name="advanced">

to

<fieldset
    name="advanced" description="test">

Currently, the description isn't shown, after the patch is applied it will show.

Known Limitations

This patch only covers "custom" fieldsets. The basic ones (like basic, description, request) are threated differently in the code and thus need to be taken care seperately.

Tracker

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32958

[Bakual]

New one against staging: #3048