Simplify settings UI and hide recycle bin section from portal settings by default

Simplify the UI so that at the portal/installation level it's only possible to enable or disable the recycle bin completely.

We want to hide this from portal settings because disabling it while the portal is running is potentially dangerous since it disables access to content which may be in the recycle bin of the existing sites. However we leave it implemented so that if for any installation it is really wanted, it's just as easy as adding it to a portal.properties property.