assets: bundles cleanup per request

* Stores bundles on request context stack.  (closes #2290)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
deposit: fix PLUpload in IE9

* Enables 'html4' runtime in PLUpload.

* Forces IE9 standard mode.  (PR #2299)

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>