Python API documentation generation tool Code

- Changed ValueDoc.pyval_repr and summary_pval_repr to return
ParsedDocstring's instead of string. These ParsedDocstrings are
generated by epydoc.markup.pyval_repr. Instead of returning a
separate value to indicate whether there's left-over (for
GenericValueDoc.is_detailed), add an 'is_complete' attribute to
the parsed docstring.
- Defer importing of dotgraph from epydoc.markup.epytext to avoid
a circular dependency.

- All tests pass again.

- The parse representation is preferred if repr() returns a stock result,
i.e. something like '<ClassName instance at 0x12345678>'.
- Using LaTeX package fancyhdr instead of the deprecated fancyheadings.
- Added missing escaping of LaTeX parameter default.
- Dropped parse_repr/pyval_repr check in HTML parameters default.

- Docstring fixed.

- Fixed docstring typo

- Warn if @type is used in a bad context.

- Removed unnecessary <code class="pyval">...</pyval> wrapping element
from the output of the PyvalColorizer.

- Modified pyval_repr.py so now it generates a ParsedEpydocDocstring
as its output. This should make it possible to change
APIDoc.pyval_repr to return a ParsedDocstring instead of a str.
This ParsedDocstring would be the result of colorization via
pyval_repr, with the parsed repr as a fallback.

- Added preliminary repr tests

- Refactored some test functions