Add pooling options to the connection strings for Postgresql

[SimonAnnetts]

In appsettings.json and appsetting.Development.json in a new cloudscribe project from the template, where Postgres is the selected EF storage option, add the following options to the example connection string:

Pooling=true;Minimum Pool Size=0;Maximum Pool Size=20;

This will enable connection pooling and sharing and reuse for Postgres database connections.