Refs #13677 - Ability to set memcached default lifetime

- Ability to set memcached default lifetime, which by now was hardcoded
  to one hour (3600 seconds). Go to ZMI > portal_properties >
  site_properties add an **int** property called
  **memcached_defaultLifetime** and set it's value to
  **86400** (one day) or any value that fits your needs.