Fix: remove usage of key_map in meta_key
Include only MetaDatumMetaTerms meta_keys into vocabulary
Admin interface: keyword list and tests thereof

Squashed commit of the following:

commit 2e9e601999325f795c2c172a72d7ee25c73c9f50
Author: Michał Podlecki <m.podlecki@op.pl>
Date:   Mon Jun 9 13:26:28 2014 +0200

    Squashed commits:

    - Admin interface: keyword list
    - tests for keyword list
    - delete searchable field and create indexes directly on the term field