Easier 32 64 bit switch

This branch makes progress toward factoring out the 32-bit/64-bit floating point types.  It's not as great as a global flag, but I think it's able to do what we want for now.

As of this commit the project still runs with 64 bit.  If you want to change it to 32 bit, run 

sed -i -e 's/float64/float32/g' $(find . -name '*.py')

in the spike directory, or run

sed -i -e 's/float32/float64/g' $(find . -name '*.py')

if you want to go from 32 bit to 64.  


The tests will fail if you use 32 bit.