Adding deleting moving drag-dropping RequirementGroups and ParameterGroups

[lxatstariongroup]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of the COMET-IME
• I have searched open and closed issues to ensure it has not already been reported

Description

We experience some strange behaviour when editting ParameterGroups and RequirementGroups.
The UI does not reflect the correct tree structure, especially after deleting a group, or nested group both for Requirements in the RequirementBrowser and ParameterGroups in ElementDefinitionBrowser.
Underlying Requirements, or groups and ElementDefinitions and groups sometimes are removed completely from the browser.
The user needs to reopen the browsers to see the correct tree structure.

I think it will be good to check all (including all crud actions) and make sure all actions work correctly.