ES filter-map: can't perform a case sensitive query

[ereteog]

In the module clj-momo.lib.es.query, the function nested-terms applies lower-case to all string values. As a consequence, it is impossible to perform case sensitive queries and to query fields that have not the lowercase filter in ES.
Since this library has now a generic purpose, we should remove that in a further version, which implies to update projects that use it.