* [ufo2map] perform value checks for epairs in SetKeyValue, too

* ... by using AddEpair
* [ufo2map] directly assign the variable
* [ufo2map] initialize the ump entity string
* [ufo2map] fixed CheckEntities

* introduced in 1d44ad3e2e62738617550107c27be268c70c6b92
* fixes bug #5338 (ufo2map doesn't recognise some properties)