Add python docstrings to boost:python bindings

[artem]

Add missing doc strings to core objects e.g Style,Rule,Filter,Datasource etc.

[springmeyer]

I think this is really, really important.

I could help with this given a bit of guidance from those familiar with boost python syntax. Perhaps we could focus on one set of really good docstrings for say:

import mapnik
help(mapnik.Map)

To use as a guide to follow.

Thoughts?

[springmeyer]

First attempt at a draft example of boost::python docstrings (this one for mapnik.Layer)

[springmeyer]

The sample patch tries to do a few things I'd like feedback on:

1) Reorders the def and properties in the order the user sees them when they call help(mapnik.Layer), just to make it easier for the docstring writer to make sure all things are accounted for. 2) Implements the convention of 4 space indents (I'm not sure how the rest of mapnik C++ code works but I'll look around) 3) Adds docstrings to the init() function as well as class functions 4) Adds sample usage with a few comments

I'm hoping to understand the best approach with the Layer class as an example, so any further work can be systematic...

[springmeyer]

Docstring for map object in boost::python

[springmeyer]

layer docstrings committed in r763 map docstrings committed in r767

[springmeyer]

r768 shows some tab fixes for the python docstrings in source:trunk/bindings/python/mapnik_map.cpp which I'll check out and try to match in the other files.

Today I also skimmed http://www.python.org/doc/essays/styleguide.html which looks like it will provide some further guidance on how to write appropriate docstrings

[springmeyer]

Cool... lots of options: http://www.boost.org/doc/libs/1_37_0/libs/python/doc/v2/docstring_options.html

[springmeyer]

And examples: https://svn.boost.org/trac/boost/browser/trunk/libs/python/test/docstring.cpp