Fix for issue 1442.

This change introduces a new style-sheet which generates
en_US property files containing all the description elements
from the XML configuration definitions. In order to expose
these properties the admin framework APIs have been modified
as follows:

   * managed object definitions
         o user friendly name
         o user friendly plural name
         o synopsis
         o description

   * property definitions
         o synopsis
         o description
         o unit description (for integer properties)
         o value descriptions (for enumeration properties)
         o pattern descriptions (for string properties). This is pretty
           much useless at the moment since the string property
           definition class does not support patterns (even though the
           XML schema does): issue 1523
         o alias default behavior description

   * relation definitions
         o synopsis
         o description
         o user friendly name (usually the user friendly name of the
           referenced managed object)
         o user friendly plural name for one-to-many relations (usually
           the user friendly plural name of the referenced managed object)

Since there is currently only weak API support for required admin
actions (issue 1426), the admin action descriptions cannot be exposed
through any API at this stage.

For I18N, translators are expected to take the generated property
files and translate them into localized versions.