Fix issue 1831: dsconfig interactive mode.


Overview:

This change completes the dsconfig interactive mode. dsconfig
now supports two levels of interactivity:

1) Usage: dsconfig

   A top-level menu driven text based console. Using
   this interactive mode the user is able able to perform
   multiple administrative tasks via a menu-driven
   interface

2) Usage: dsconfig <sub-command>

   dsconfig will perform the administrative task
   associated with the specified sub-command prompting
   the user for any missing information required in
   order to complete the task

In addition, both interactive modes will prompt the user
for any connection parameters not specified on the command
line.

Note that it is possible to run dsconfig non-interactively
using the "-n" option. Although this is only available when
a sub-command is provided.


Other changes:

1) part of this work required implementing a generic CLI
application framework. This includes an API for building
and running menu-based interfaces. The classes are located
in a new package called org.opends.server.util.cli

2) the dsconfig related messages have been relocated into
a separate dsconfig-specific properties file.