Index municipality names as keywords instead of as plain text. This prevents
them from being split at word separators. Thereby avoiding that searches for a
municipality name, as used by the frontend's municipality filter, return
organisations whose municipality is a partial match.
For example, previously the results when searching for "Puurs" also included the
organisations located in "Sint-Amands-Puurs". The latter was tokenized into
three terms, therefore also matching plain "Puurs". By treating the municipality
name as keyword this split non longer happens.
Soon we want to introduce (additional) non-administrative unit
organizations. This renaming makes it more clear this index is not limited to
administrative units, both here as where it is used in the frontend. Note,
technically the 'units' name was already incorrect as a 'Representatief orgaan'
is not an administrative unit.
