Expandable Standard Panel and Standard Listing Panel

[tfamula]

This PR introduces an extension to the Standard Panel and Standard Listing Panel to make them expandable, as it is need for https://docu.ilias.de/goto_docu_wiki_wpage_7416_1357.html. The PR includes the interface changes and also the implementation part of it.

The following things are missing and will be added if interface ~~and implementation are~~ is accepted:

• [x] CSS adjustments for the Bulky Buttons in the Panel header (including the requirement in the FR: "[...] the clickable area should be as large as possible so that the user can also click next to the panel title to open or close it.")
• [x] Adding / fixing unit tests

~~Please also consider, that the Javascript part was tested on ILIAS 9, since Javascript is not working yet on current trunk.~~