feat(tfgrid3deployer): add delete method for deployments

- add a delete method for deployments which deletes all deployment
  contracts
- improve logging messages
- update examples according to changes

examples/threefold/tfgrid3deployer/vm_gw_caddy/delete.vsh

@@ -12,13 +12,4 @@ v := tfgrid3deployer.get()!
 println('cred: ${v}')
 
 deployment_name := 'vm_caddy1'
-mut deployment := tfgrid3deployer.get_deployment(deployment_name)!
-deployment.remove_machine('vm_caddy1')!
-deployment.deploy()!
-os.rm('${os.home_dir()}/hero/db/0/session_deployer/${deployment_name}')!
-
-deployment_name2 := 'vm_caddy_gw'
-mut deployment2 := tfgrid3deployer.get_deployment(deployment_name2)!
-deployment2.remove_webname('gwnamecaddy')!
-deployment2.deploy()!
-os.rm('${os.home_dir()}/hero/db/0/session_deployer/${deployment_name2}')!
+tfgrid3deployer.delete_deployment(deployment_name)!

examples/threefold/tfgrid3deployer/vm_gw_caddy/vm_gw_caddy.vsh

@@ -29,12 +29,9 @@ println('vm1 info: ${vm1}')
 
 vm1_public_ip4 := vm1.public_ip4.all_before('/')
 
-deployment_name2 := 'vm_caddy_gw'
-mut deployment2 := tfgrid3deployer.new_deployment(deployment_name2)!
-deployment2.add_webname(name: 'gwnamecaddy', backend: 'http://${vm1_public_ip4}:80')
-deployment2.deploy()!
-
-gw1 := deployment2.webname_get('gwnamecaddy')!
+deployment.add_webname(name: 'gwnamecaddy', backend: 'http://${vm1_public_ip4}:80')
+deployment.deploy()!
+gw1 := deployment.webname_get('gwnamecaddy')!
 println('gw info: ${gw1}')
 
 // Retry logic to wait for the SSH server to be up