Change Latin Square version to work with PsiTurk.

Latin Square version used to be random. Now it's grabbed from the
webpage. PsiTurk will supply it as a variable called condition. It also
allows the use of another variable called counterbalance but I haven't
created a way of using both. It is no longer possible to have different
group sizes in different latin squared blocks.
Add makeJSON.py so you can write in Python.

makeJSON.py provides objects so you can write a Python script to
generate a JSON file. It's currently for convenience but not validation.