functions: Generate functions dynamically from a list

This reduces the boilerplate code that is needed to define new functions.
doc: Adjusted inline code padding
functions: Added docstrings to Geometry Accessors
functions: Add PostGIS documentation links to docstrings
doc: Hide inheritance of spatial functions

The documentation of the GenericFunction class states this very prominently
and mentioning it over and over again is only visual clutter.
functions: Adjusted Geometry Accessors documentation format

The triple quotes were having some side effects.
functions: Added docstrings to Geometry Editors and Outputs
functions: Added docstrings for the remaining functions
doc: Disabled documenting of attributes without docstrings

only for geoalchemy.functions module
functions: Python 2.6 compatible format() calls
Merge pull request #35 from Turbo87/functions

functions: Generate functions dynamically from a list