gnu: Move database packages from python.scm to databases.scm.
* gnu/packages/python.scm (python-ccm, python2-ccm, python2-pysqlite,
python-sqlalchemy, python2-sqlalchemy, python-sqlalchemy-utils,
python2-sqlalchemy-utils, python-alembic, python2-alembic,
python-pickleshare, python2-pickleshare, python-apsw, python2-apsw,
python2-neo4j-driver, python2-py2neo, python-psycopg2, python2-psycopg2,
python-sadisplay, python2-sadisplay, python-mysqlclient,
python2-mysqlclient, python-hiredis, python2-hiredis, python-fakeredis,
python2-fakeredis, python-redis, python2-redis, python-rq, python2-rq,
python-trollius-redis, python2-trollius-redis, python-sqlparse,
python2-sqlparse, python-sql, python2-sql): Move from here...
* gnu/packages/databases.scm: ...to here.
* gnu/packages/tryton.scm,
gnu/packages/python-web.scm,
gnu/packages/nutrition.scm,
gnu/packages/medical.scm: Adjust accordingly.
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