Add support for BUCKETTIMESTAMP and EMPTY range paramters

[nerg4l]

In version 1.8 of RedisTimeSeries BUCKETTIMESTAMP and EMPTY parameters were added to TS.RANGE, TS.REVRANGE, TS.MRANGE, and TS.MREVRANGE commands.

Additionally, BUCKETTIMESTAMP, EMPTY, and ALIGN parameters only allowed when AGGREGATION is set. Maybe a new structure could enforce this.