Filterset improvements

[algorithmiker]

• fix en_filterset_not: en_filterset_not(en_filter("message", "EQ", "foo", en_filterset_from_range(en_span_range()))) fails to evaluate
• lua api rewrite: en_filterset_not -> en.filterset.not where en.filterset is a global module
  • This might not work, as it'd break autocomplete? Long term goal for sure
• add en.filterset.root = en_filterset_from_range(en_span_range())
• rename to logical instead of set terms (eg. union -> or)