stype: Commented out warnings about "deprecated" usage of "value slots".
Opened ilastik/ilastik#704, related to this.
Memory Manager: Init mem_usage to mem usage at app startup.
slot.value: Handle case where value is an iterable other than a list.
This fixes the particular issue observed in ilastik/lazyflow#76, which involved a "value slot" where the value is a dict.
This issue needs to be fixed more generally.  See also: ilastik/ilastik#704 and ilastik/ilastik#705
stype: Removed a warning from Opaque.writeIntoDestination().
Filed an issue concerning the warning that was removed, and added a comment explaining the issue.