Added L1WeightDecay class to dbm costs and get_l1_weight_decay for BinaryVectorMaxPool layer class.
Small typo fixed in get_l1_weight_decay
Fixed the l1 weight decay to use abs, not T.abs
Added and fixed l1 weight decay in BVMPLayer.
Added L1 weight decay to BVMP.  Will add to other layers as well soon.
Refactored GaussianVisLayer tests into a class.
Refactored GaussianVisLayer into a stand alone class.  Duplicate code removed for clarity and some documentation added.