New post_office chunks should be improved

[jajajaneeneenee]

The new chunk "post_office" is only used with amenity=post_office, and the second chunk "post_office_optional" is used for all items which could have integrated a post office / offer postal services on behalf of a postal service provider (like shop=kiosk).

But for a amenity=post_office, the key brand should be used, not post_office:brand, which is contained in the "post_office" chunk. (See Wiki: _"On an object with amenity=postoffice, please use the key brand=*).

Therefore I would suggest to change the two post_office chunks like this (included are some text change suggestions):

OLD:

    <chunk id="post_office">
        <combo key="post_office" text="Post office type" values_searchable="true">
            <list_entry value="bureau" short_description="Full post office"/>
            <list_entry value="post_annex" short_description="Full post office operated by 3rd party"/>
            <list_entry value="post_partner" short_description="Postal services provided"/>
        </combo>
        <text key="post_office:brand" text="Postal services brand" />
    </chunk>
    <chunk id="post_office_optional">
        <optional>
            <reference ref="post_office"/>
        </optional>
    </chunk>

NEW:

    <chunk id="post_office_types">
        <combo key="post_office" text="Post office type" values_searchable="true">
            <list_entry value="bureau" short_description="Full post office"/>
            <list_entry value="post_annex" short_description="Full post office operated by 3rd party"/>
            <list_entry value="post_partner" short_description="Postal relay point with some services"/>
        </combo>
    </chunk>
    <chunk id="post_office_integrated">
        <optional>
            <reference ref="post_office_types"/>
            <text key="post_office:brand" text="Postal services brand" />
        </optional>
    </chunk>

And to add the key brand to the amenity=post_office item ("Post Office").

(And I would also add brand:wikidata keys, which is often used with post offices, i.e. post_office:brand:wikidata for the chunk "post_office_integrated" and brand:wikidata for amenity=post_office.)