Allow copying of POIs

[osmers]

Motivation

If the description of a POI is the same for multiple POIs, e.g. for pharmacies or Kleiderkammern, copying the POI and simply changing the address is a big help.

Proposed Solution

Add the option to copy POIs, same as for events.

Alternatives

Keep it, as it is.

User Story

As a CMS user I would like to be able to copy POIs with the same description to save time on copy and pasting.

Additional Context

Implement this function