Various fixes to website content.

include/menubar.inc:
    Disable the downloads submenus for now.  Until we fix the downloads page
    more permanently it is best to disable these submenus in the website as
    they may confuse visitors.

documentation/include/deep_demo.inc:
    Say that the deep profiler has been available since 10.04

development/include/developer.inc:
    Warn about out-of-date developer's information.

include/contact.inc:
    Add an e-mail address to the contact page as there may be cases where
    the mailing lists aren't appropriate.
Add links to other communties

include/contact.inc:
    Add a number of links to Mercury communities on the web.