Python API documentation generation tool Code

- refactored class_tree_graph & uml_class_tree_graph -- now they share
most of their code.
- added truncation when class graphs get too big: max_subclass_depth
truncates subclasses that are too far down in the tree, and
max_subclasses limits the number of subclasses that are shown for
any given class.
- undocumented base classes are now drawn with a grey background
- uml graph options:
- Changed default values for max_attributes & max_operations
- Added options to control whether parameter defaults are shown;
and to truncate signatures that are too long
- set minimum width for uml nodes to 100
- Fixed bug in DotGraphNode -- subclasses should share the same
_next_id var, not use their own.
- If dot fails & epydoc.DEBUG is true, then print the broken dotfile
to a temp file.

- Always write the subclass list, even if the class tree is drawn.
I plan to truncate large class diagrams, so the list will be
useful in those cases.

- If a class's metaclass is known, then show that class instead of
'Class' on its class html page
- When displaying class description tables, don't bother with the
'type' column -- it's always empty anyway.
- If a property's fget/fset/fdel function has the name '??', then
don't bother to list it.

- Added 'metaclass' var to ClassDoc, to record the metaclass (when
defined)

- Minor changes to TerminalController class

- Added support for the syntax `name <target>` in rst interpreted
text roles.

- Added support for the syntax `name <target>` in xlink.

- If the source file is not encoded correctly, then issue an error
(rather than crashing) and give up on parsing.

- Minor css fix for subclass list

- If the source file is not encoded correctly, then recover as well
as we can, and issue a warning.