Clean option drops entire mongo database

[Lewwwk]

Currently, passing the clean option to load or create drops the entire mongo database. This can cause disastrous effects.

Expected Behavior

Clean should only drop the facts collection in the database and not affect the rest of the database. Currently, that collection is called mongodown.

Current Behavior

Currently it executes db.dropDatabase() when clean is specified.

Possible Solution

Changing to db.mongodown.drop() would drop only the collection.

Steps to Reproduce (for bugs)

Can test by creating a superscript bot, triggering an action that would create a fact, then triggering a load or create action with clean=true

Context

If triggered unexpectedly, it could cause catastrophic data loss.

Your Environment

All the shiniest node, mongo, superscript.

[hailiang-wang]

sfacts has dropped all data

This is not reasonable. This PR seems good to me.