ns_cluster:counters()/counter_inc() API
ns_cluster:counters()/counter_inc() API

Change-Id: Iccf671c8c964b09246fd7b18f401fa4279156559
Reviewed-on: http://review.couchbase.org/11441
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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