reduce memory footprint

I'd like to run huge (human like region) CLA instance. CLA is not really mem optimized, this is some initial work. 

Highest pressure should be applied to the most commonly used parts - Column-Cell-Segment-InSynapse. 

*) Last commit removes unused field frequency from Segment and all it's occurences. This should simplify the code and reduce mem as well. 

*) Other patches change InSynapse->permanence to float (from Real==Real32/64==double). I don't change the definition of Real globally (some high precision demands) but esp. permanence makes quite "low-grained" steps (eg +-0.1). 
I'd even like yours input on reducing it to byte (and assumin /255 internally) so we'd have 255 steps between 0..1 for perm.