added CHANGES files and listed all significant 1.8.1 changes
added CHANGES files and listed all significant 1.8.1 changes

Change-Id: If48a925070143d23be171b40c544bd9293ff41f0
Reviewed-on: http://review.couchbase.org/15422
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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