Fixed up some issues, added optimization space.

Fixed some errors I found in the prior PRs, added SparseVector transpose stuff, with implicits, and added an Optimization Space that combines Matrix and Vector implicit ops into one object, and gave a shortcut for using Dense and Sparse Optimization spaces. 

Let me know what you think, and feel free to merge everything except for the Optimization Space.. I'm using it in my Nak NCA code since it makes things easier, but as I mentioned is kind of a hack and it would probably be better to use something like the combine macro that I described. If I get around to it, I'll PR that into breeze-macros and remove the OptimizationSpace code.