Extend the handling of type

[yehudarav]

Currently, we handle only type float and string. That is, the properties must be converted to their type
and not kept as string. Should also be taken care of in dates and ect.

[yehudarav]

See fillContained lines 37,47

@erasta The mechanism isa suggestion, i guess you will have a better idea.
I usually place everything in classes, and then it is east to use getattr("handle_{type}") . It makes the manual
maintaining of the type dict reduntant.