Advanced properties phase 1: tag advanced properties and perform
various clean-up to the XML definitions:

   * clean up typos and any bad grammar in the synopsis/description
     elements

   * fixed common errors. For example, there were many places where the
     synopsis was repeated in the description (the description is only
     ever used in conjunction with the synopsis). There were also many
     places where the <adm:user-friendly-name> was being used in
     property definition description elements to refer to the property
     name, when it actually refers to the managed object name

   * split big synopsis (not sure of the plural form - synopsi?) where
     possible - there were lots of cases where we'd have a big synopsis
     but no description

   * overrode properties with sensible default values where
     appropriate (for example, I provided sensible default values for
     some of the attribute-type properties in the virtual attribute
     definitions)

   * generally made documentation more consistent across the definitions

   * removed unneeded XML attributes of the form 'mandatory="false"'.
     Attributes only need to be specified if their value is true as
     they default to false. Adding redundant attributes just makes the
     XML harder to read

   * removed any documentation that referred to the configuration in
     LDAP related terms (with one exception in the Schema backend). All
     documentation now refers to other properties using the property
     names, not their associated LDAP attribute.