Make travis logs on the console only.

Currently travis also logs to the file and MongoDB, but it's useless.
Logging on the database.

Currently, beyond logs to the file and console. We need to save the log
on the mongodb.

This patch makes beyond depend on the logback-contrib, because MongoDB
Appender is not implemented in the logback-core but in the the
logback-contrib.
Add `use-sharding` option for MongoDB.

Currently Beyond launches a standalone MongoDB server on
localhost. This patch renames the current MongoDBLauncher to
MongoDBStandaloneLauncher and makes Beyond use it only when
`use-sharding` is false.

Sharding itself hasn't been implemented yet.
Separate a common part of MongoDBStandaloneLauncher.

Some part of MongoDBStandaloneLauncher can be used for other MongoDB
instances such as shards or config servers. This patch separates the
part into MongoDBLauncher.