Do not hardcode the image representation of an IMBNodeObject to large generic folder icon

To have image representations on a per node Object basis is a better default (so we can use it for subnode objects of the me node in Facebook parser)
Restrain concurrency of requests to parsers to maximum of 8 threads

We had instances where the Facebook parser hung up on us when about 60 some parallel requests were issued (this might correlate with the fact that all Facebook requests reach out to the internet).

Going beyond eight parallel resources did not seem to gain any better performance on any of the parsers.
Fix memory leak