adding exp-val-z calc (taken from qpp) to aer statevector mode. updating...

adding exp-val-z calc (taken from qpp) to aer statevector mode. updating internal_compiler setAccelerator to parse NAME:BACKEND[KV_OPTS] string, useful for qcor command line

Signed-off-by: Alex McCaskey <mccaskeyaj@ornl.gov>
3 jobs for master in 70 minutes and 11 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Deploy
passed docker run_docker_deploy #619929

00:14:42

passed docker run_docker_xacc_qcs_deploy #619931

00:19:02

passed docker run_docker_xacc_quac_deploy #619930

00:36:26