Description Plugin: Ability to edit description with Markdown editor

**Context**

Currently, the Description Plugin content can only be edited through the Advanced Plugin where a Markdown editor is located. This could be made much easier by providing this functionality directly int he Description Plugin.

**Acceptance Criteria**
- Users with Read access can still see the Markdown rendered description as before.
- For users that have Write access to the underlying Nexus Project, allow user to open the Markdown editor and edit the description.
- There is a clearly visible way to open the edit mode and potentially to cancel ongoing edit.
- Description tab should be removed in the Advanced View Plugin
- Given the above, the Description plugin should always be shown, irrespectively of a description being present.

Start by locating the Description Plugin and Advanced View Plugin, then trace how the existing Markdown editor is exposed and how write access to the underlying Nexus Project is checked. Implement the acceptance criteria for rendering, edit and cancel controls, plugin visibility, and removal of the Advanced View description tab; verify both read-only and write-access behavior.

Written by the indexing model from the issue text.