If we want to use construct parse results to generate JSON serializable
dicts, we need to
* apply the filter_dict() operation recursively, and
* simplify the construct Container and ListContainer classes to
a simple dict and/or list.
We introduce a pySim.construct.parse_construct() helper which is
subsequently used from all pySim.filesystem caller sites.
Change-Id: I319414eb69808ef65895293832bb30519f45949d