[BPM] colormaps/scaling/stuff

The Bpm.construct_bvdata function needs some work. I get a null image and no profiles when using limagui (hooked on the bvdata tango attribute)

Not sure what the scaling is supposed to do, but with the simulator it just flattens the image to 0. The profiles are sent as a string representation of the array (e.g: '[1, 2, 3]'), instead of an encoded byte array like it's done for the jpeg data.