app/testpmd: clean metering and policing commands

app/testpmd: clean metering and policing commands

This patch updates the metering and policing CLIs as follows:
- change name of set port meter CLI to create port meter and add meter
  enable option, dscp table entries arguments, action mask, policer actions
  and previous meter color option as an input color
- set the right metering algorithm in add meter profile CLIs related to
  srtcm(rfc2697) and trtcm(rfc2698,rfc4115)
- change clear flag type from uint32_t to string in show meter stats CLI

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>