Description Plugin: Ability to edit description with Markdown editor

[samuel-kerrien]

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.