Revised documentation.

Fixed several errors in the "more sophisticated tab view hierarchy" example.
Fixed wrong attribute name in navigation template example.
Fixed quotes in include template tag example.
Updated the warning because Ticket #16074 is part of Django 1.5. \o/
Separated links and target definitions (for better readability of the RST sources).
Changed line length to 72 characters (PEP 8).
All links to the Django documentation use 1.4 instead of dev.