CBQE-363: add methods to get ram/cpu/memory info

Methods gets these info based on systeminfo batch command

Change-Id: I31fe841d6823b89ca3c6577d131a2d17997b9cf0
Reviewed-on: http://review.couchbase.org/18728
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>