Updates to allow aggregator to host non-aggregated app resources.

This update enables defining resource alias paths to be served by the aggregator, thus allowing both aggregated and non-aggregated static resources to reside beneath the aggregator servlet alias namespace, eliminating the need for externally defined resource servlets (e.g. org.eclipse.equinox.http.registry.resources).

The sample app has been updated to support both modes of operation.  The traditional mode uses the aggregator only for aggregating resources and serves non-aggregated resources (e.g. when using test-no-aggr.html) from the resource servlets defined in the resource bundles.  This mode is loaded with the URLs [http://localhost/test/res/test.html](http://localhost/test/res/test.html) and [http://localhost/test/res/test-no-aggr.html](http://localhost/test/res/test-no-aggr.html).  Using the new mode, the app namespace resides entirely within the test/aggr namespace, with the aggregator serving both aggregated and non-aggregated resources.  This mode is loaded with the URLs [http://localhost/test/aggr/app/res/test.html](http://localhost/test/aggr/app/res/test.html) and [http://localhost/test/aggr/app/res/test-no-aggr.html](http://localhost/test/aggr/app/res/test-no-aggr.html).  Both modes of operation are supported concurrently.

This pull request includes some interface changes relating to aggregator initialization and InitParams.  This was necessary to support multi-valued init-params, which the previous interface did not allow and which is needed for defining aggregator resource aliases.