Revision 889469

TAP5-815: Asset dispatcher allows any file inside the webapp visible and downloadable
Backport changes from trunk to 5.0: 404 returned instead or 403 for restricted assets; add a new integration test; fix AssetProtectionDispatcher unit test. 
Note that opening up context assets is unnecessary for the 5.0 branch because it handles context assets by generating a url for them that is handled by the servlet container, rather than the AssetDispatcher.