mfsCommon encode atom

[lpatiny]

The content of 'atom' should not be a Stringified version of the object.

> db.mfsCommon.findOne()
{
    "_id" : "B10",
    "em" : 110.0930536,
    "unsaturation" : null,
    "atom" : "{\"B\":10}",
    "count" : 8
}