Migrate to PostgreSQL

[felipemoraes]

At moment SearchX makes use of MongoDB to store logs and helper data.
SearchX is highly dependent on MongoDB and in a future version we intend to migrate it to PostgreSQL.

Recently, MongoDB has changed its license and that means that anyone that uses MongoDB should open-source the service to give back the community. We understand that this is a limitation in which if anyone that wants to use SearchX in a private sector needs to migrate to the data storage.