Refactor data_transform to allow datum, cv:Mat and Blob transformation

Move data_mean into the data_transform class to facilitate data transformation. 
This way Data layers don't need to hold it and pass it all the time. 

@bhack the OS X BVLC members are going meet about this soon -- a likely
compromise is to disable in-memory OpenCV input for OS X but build it on
linux until we can figure out how to make it all fit.

On Thu, Sep 25, 2014 at 10:40 AM, bhack <notifications@github.com> wrote:

> In include/caffe/data_transformer.hpp:
>
> >     * @param datum
> >     *    Datum containing the data to be transformed.
> > -   * @param mean
> > +   * @param datum_vector
>
> Ok but it is very hard to refine this with only one developer testing on
> OSX. We doesn't have a osx build server. Probably this feature will never
> go in.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/BVLC/caffe/pull/1070/files#r18047001>.
>