[cells.js] allow futures to continuously deliver stream of values
[cells.js] allow futures to continuously deliver stream of values

This also includes simplest use of this facility: futures.pollingGET

Change-Id: Ie474b70cba0e71951d6287fcd5686990fe223be6
Reviewed-on: http://review.northscale.com/875
Reviewed-by: Eric Lambert <7ef4e71cebb32cb5e304f9d7d27d812f8d7da939@gmail.com>
Tested-by: Eric Lambert <7ef4e71cebb32cb5e304f9d7d27d812f8d7da939@gmail.com>

mschoch/ns_server,vzasade/ns_server,ceejatec/ns_server,daverigby/ns_server,membase/ns_server,vzasade/ns_server,nimishzynga/ns_server,daverigby/ns_server,vzasade/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,daverigby/ns_server,ingenthr/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,vzasade/ns_server,mschoch/ns_server,mschoch/ns_server,membase/ns_server,ingenthr/ns_server,ceejatec/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,membase/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,pavel-blagodov/ns_server,pavel-blagodov/ns_server,membase/ns_server,ingenthr/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,nimishzynga/ns_server,mschoch/ns_server,ceejatec/ns_server,membase/ns_server,daverigby/ns_server,nimishzynga/ns_server,ingenthr/ns_server,membase/ns_server,mschoch/ns_server