[Tagging] religious place for any religion/multiple religions

[Mateusz Konieczny]

There are religious places that are not for any specific religion (for
example universal "place of contemplation" at some airports or place of
worship at cemetery, possible to be used for any funeral-related
religious ceremony)

There may be also place used by some set of religions.

I would expect that religion=multifaith is used for the first purpose.

I would expect that ;-separated list would be used for the second
purpose.

But religion=multifaith is documented on wiki only as "Multiple
religions" on https://wiki.openstreetmap.org/wiki/Key:religion what is
not clear.

; separation is not mentioned at all at
https://wiki.openstreetmap.org/wiki/Key:religion

I plan on 

- properly documenting religion=multifaith as described above
- document ;-separated values as acceptable for religion tag and
  recommended if object is really shared by multiple religions

Is there anything wrong with that?