PostgreSQL templates are out of date

[101-webapp-linux-managed-postgresql](https://github.com/Azure/azure-quickstart-templates/blob/master/101-webapp-linux-managed-postgresql/azuredeploy.json)

### Issue Details
"apiVersion": "2016-02-01-privatepreview" does not allow creation of Gen5 machines.

### Repro steps (*if necessary, delete otherwise*)
1. Set SKU Name to 'B_Gen5_2'
2. Deploy. Error returned

I would expect this example to be current and provide parameters that include allowedValues which allow the deployment to succeed.

Start with 101-webapp-linux-managed-postgresql/azuredeploy.json and inspect the PostgreSQL apiVersion, SKU parameter, and its allowedValues. Deploy the template using SKU Name B_Gen5_2 and verify that the updated parameters allow the deployment to succeed.

Written by the indexing model from the issue text.