PSTD
Docs: docstrings updates to room acoustics module
Docs: docstrings updates to reflection, turbulence, octave and power.
Docs: new structure
Merge pull request #16 from FRidh/docs

Docs: new structure and updated docstrings.
PSTD
Turbulence: Change indexing for calculation of field.

Generating a field of size (x,y) resulted in a shape where the
dimensions were ordered as (y,x). This patch changes the ordering from
cartesian indexing to matrix indexing.

A very simple test is included as well to test whether object creation
and field() execution goes without issues.
Merge branch 'master' of github.com:python-acoustics/python-acoustics into pstd

Conflicts:
	docs/reference.rst