Many resources with file scheme return error

Many resources with file scheme return error

[Title] When lots of images (over 1000) with file scheme are loaded, they dont load properly
[Issue#] DCM-2062, WEB-3382
[Problem] Resource load scheduler limits number of requests to 20, but it does not work for file scheme.
          Since kernel limits the number of files open to 1024 at any moment, loading fails with error "Too many files".
[Cause] When file scheme is used, the resource limit is lifted off when parsing of document is completed
[Solution] Limit requests of every scheme, but raise the limit to 512

Change-Id: I22977fde46391fa52dfaf3259101ca4f8d557a9f