The amount of data transferred by the history.get call can be quite overwhelming on network resources when transiting between remote locations and a central interface.

This patch adds the ability to get the output compressed where values are the same, e.g

itemid:1 clock:1000000: value:1
itemid:1 clock:1000001: value:1
itemid:1 clock:1000002: value:1

becomes
itemid:1 clock:1000000: value:1
itemid:1 clock:1000002: value:1

when compressValues is supplied to the history.get call.

This has drastically reduced out output sizes (from 100,000+ items per day in request) to 10-20 with the same or better resulting graphing quality.

This patch does not impact any other features if this option is not provided.

Could this be included?