Major fixes for RasterPlot
Major fixes for RasterPlot

Raster types now oriented correctly, support matplotlib cmaps
and extents are correctly defined.

vascotenner/holoviews,basnijholt/holoviews,vascotenner/holoviews,mjabri/holoviews,ioam/holoviews,ioam/holoviews,basnijholt/holoviews,vascotenner/holoviews,mjabri/holoviews,basnijholt/holoviews,ioam/holoviews,mjabri/holoviews