Allow labels and annotation field validation

[yaacov]

Fixes: #25

Before:

16:30 $ kubectl-sql "select name, status.phase, annotations.security.openshift.io/validated-scc-subject-type as scc from */pods"
Error: invalid field identifier before AS: annotations.security.openshift.io/validated-scc-subject-type
Usage:
  sql <query> [flags] [options]
  sql [command]

Examples:
  # Print client version.
  kubectl sql version

After:

16:29 $ kubectl-sql "select name, status.phase, annotations.security.openshift.io/validated-scc-subject-type as scc from */pods"
KIND: Pod	COUNT: 446
name                                                           	status.phase	scc           	
openshift-apiserver-operator-558c446987-f4h77                  	Running     	serviceaccount	
apiserver-587d568646-bvmbp                                     	Running     	serviceaccount	
apiserver-587d568646-gk8ll                                     	Running     	serviceaccount	
apiserver-587d568646-l774l                                     	Running     	serviceaccount	
authentication-operator-5855f5d9b4-6szrm                       	Running     	serviceaccount	
oauth-openshift-6f5fdcbc8f-ft5bj                               	Running     	serviceaccount