Moving to unordered dict, better data type management

[raamana]

[raamana]

this may create a problem with backward compatibility - previous versions saved the dataset with OrderedDict, so I need handle loading them in properly.

[raamana]

Also, note that the regular dict in python 3.6 preserves insertion order, however this is not to be relied upon, as it is considered an "implementation detail" today and might change later on.