[INTERNAL][FIX] re-added central entrypoint for icon explorer with redirect
[INTERNAL][FIX] re-added central entrypoint for icon explorer with redirect

Since the central URL was used on the ABAP stack we re-added the index 
page for the icon explorer with a redirect to its new location:
http://openui5.hana.ondemand.com/iconExplorer.html

Change-Id: Ifdb0dc6fb22c0ca773ed565f79445ec6b62036e7

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5