Further edits to the notes on GA and relateds notes on viscosity/density

Changes to be committed:
	new file:   Research-notes/GA-in-Python-note.lyx
	new file:   Research-notes/viscosity-and-density.lyx
Fixed name of webots world for simulation of type-1 Braitenberg-like vehicle
- Replaced computation of drag with 2 simpler functions:

  in both dragEquationDrag and stokesLawDrag, all parameters except viscosity and velocity have
  been compacted into a single viscosity parameters, yielding the two functions:

  dragEquationDrag = viscosity * velocity ^2
  stokesEquationDrag = viscosity * velocity

- Also, changed viscosity from being in the [0,1] interval
  to being in the [0,maxViscosity] interval.

- maxViscosity is set to a default value of 10 in HomeoUnit.DefaultParameters['maxViscosity']

- Changed experiments to set starting viscosity values at 0.9 * maxViscosity instead of 0.9

 On branch viscosity-improvements
 Changes to be committed:
	modified:   src/Core/HomeoUnit.py
	modified:   src/Core/HomeoUnitNewtonian.py
	modified:   src/Simulator/HomeoExperiments.py
Various comment improvements and cleanups
Merged changes from viscosity-improvements branch into master. Simplified drag computation in dragEquationDrag and stokesLawDrag functions