Added wrapAround parameter to SP 

Fixes #1211
Fixes #1216

@chetan51 please review
The previous mapping is a bit odd.  Example in a 1 dimensional case it centers the first column over the first input and the last column over the last input.  If wrapAround is on, meaning that these inputs are considered neighbors then these two columns have almost identical receptive fields unlike the rest of the columns which are spread out relatively evenly.  In the 2D case it is even worse as the four columns centered over the corners have essentially identical receptive fields.  This new approach divides the inputs up equally among columns and centers each column over its share of the inputs.