Remove psycopg1.cursor usage

psycopg1's cursor (and `dictfetch*` methods) are not bad per se, but they're not part of dbapi and make it harder to use alternative drivers (including psycopg2cffi, the psycopg2 port to cffi which works with pypy).

Reimplement `dictfetch*` in OpenERP's own cursor and move to raw psycopg2 cursors.