jruby: implement missing calls in JRubyPaymentPlugin

This also fixes compiler warnings.

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
payment: implement missing queries in DirectPaymentSqlDao.sql.stg

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
server: add more tests for direct payment APIs

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>