MXS-1929: Add create/destroy service MaxCtrl commands

Added commands for creating and destroying services. The create command
allows server and filter relationships to be defined but they are not yet
processed by MaxScale. This will be done once the use of filters is made
dynamic.

maxctrl/lib/destroy.js

@@ -45,6 +45,16 @@ exports.builder = function(yargs) {
                 return doRequest(host, 'services/' + argv.service + '/listeners/' + argv.name, null, {method: 'DELETE'})
             })
         })
+        .command('service <name>', 'Destroy an unused service', function(yargs) {
+            return yargs.epilog('The service must be unlinked from all servers and filter and ' +
+                                'all listeners for the service must be destroyed before the service ' +
+                                'itself can be destroyed.')
+                .usage('Usage: destroy service <name>')
+        }, function(argv) {
+            maxctrl(argv, function(host) {
+                return doRequest(host, 'services/' + argv.name, null, {method: 'DELETE'})
+            })
+        })
         .command('user <name>', 'Remove a network user', function(yargs) {
             return yargs.epilog('The last remaining administrative user cannot be removed. ' +
                                 'Create a replacement administrative user before attempting ' +