Added short note on contents of ChangeLog.
Fixed broken changelog formatting.
Made Inflection#morphology_tag accessible.
Split inflections.lemma into inflections.{lemma,part_of_speech_tag}.

In the inflections table the lemma column stores both the lemma base
form and the part of speech tag, separated by a comma. This moves the
part of speech tag to its own column in line with the convention
followed elsewhere in the schema.