removed psidispatcher.py. its code is long in spockplugin.py and not used otherwise.
refactored projection to define image plane by width and height rather than visual angles because floating points.
introduces a fovea patch which feeds straight to learners.
Merge pull request #59 from joschabach/refactoring-projection

Refactored the projection code
adds a fovea of size 8x8.
make fovea-related parameters independent of the size of the image plane.