HPCC-8600 Add ecl command line support for query priority

Add --priority option to ecl publish, queries config, and
queries copy.  Add display of priority to queries list.

Possible values are LOW, HIGH, SLA, and NONE.  NONE clears the
existing priority value restoring default bahavior.

Signed-off-by: Anthony Fishbeck <Anthony.Fishbeck@lexisnexis.com>
Merge pull request #3870 from afishbeck/cli_priority8600

HPCC-8600 Add ecl command line support for query priority

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>