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
doc: Enabled html_static_path variable again

This reverts commit ed770da9c0fc81e483848c60d88c4ab5732599ba.

Somehow the smaller logo wasn't copied properly anymore after the patch.
Merge pull request #36 from Turbo87/docs

doc: Enabled html_static_path variable again
Added missing license file

setup.py states license='MIT', but we should emphasize that a bit more
publicly.
Merge pull request #37 from Turbo87/license

Added missing license file
functions: Python 2.6 compatible format() calls
TravisCI: Enabled Python 2.6 testing
Merge pull request #35 from Turbo87/functions

functions: Generate functions dynamically from a list
functions: Fixed PEP8 warnings

E501 line too long
tests: Fixed PEP8 warnings
TravisCI: Added flake8 checking

E711 is ignored because "is None" does not work in SQLAlchemy's filter()
method, but flake8 warns that "== None" should not be used.
shape: Fixed buffer usage for Python 3.x

This is theoretically irrelevant since shapely is not yet compatible
with Python 3.x, but flake8 is complaining on Python 3.x that buffer is
not defined.