Moved switch to time-dependent into Model constructor

Tests and models that don't use time-dependent will break if
time-dependent is set to True on import.
Fixed pyflakes warnings
Updated param submodule reference
Started working on color
Started working on color
Change color analysis for new retina
Bugfix
Improved colorized Gaussians
Bugfixes color
Change in name of AfferentSurround and AfferentCenter projections
Bugfix from last rebase
Removed TODO's for color
Add image dataset option to VisualInputModel
Allow choosing image dataset