Use Sphinx-friendly formatting for overloaded functions documentation.

Sphinx doesn't allow sections inside the function documentation and gives tons
of SEVERE warnings for them, so while just emphasizing the "Overload" header
is not ideal, it is better than before because at least the string "Overload"
itself appears in the Sphinx-generated output.
Preserve relative indentation when parsing Doxygen comments.

This is important to preserve the structure of the lists which appear
correctly in Python output without any additional effort if the indentation is
lost.

It is also makes the behaviour consistent for

	/**
	 *
	 *
	 */

comments and those without the asterisks in the middle lines, as now the
indentation is preserved in both cases while it was only preserved when the
asterisks were present previously.
No real changes, just remove an unnecessary variable.

Avoid copying "pyDocString" to "result" completely unnecessary, just use
"pyDocString" itself directly.
Remove unused method from PyDocConverter.

justifyString() was unused and doesn't seem to be useful as there are no
particular constraints on the line length in Python documentation, so just
preserve whatever is used in the original C++ code.
Fix arguments of @param, @return etc translations to Python.

For the parameter documentation to be really taken as such, in its entirety,
by Sphinx, it must be indented relative to the :param: tag. Do this by
appending an extra indent after every line of the output and work around the
unnecessary indent of the last line by removing the trailing whitespace.

This required updating the existing tests and removing the expected but not
present any more whitespace from them, but as trailing whitespace in the
documentation is at best insignificant (and at worst harmful) anyhow, this is
not a big price to pay for simpler translator code.