We added support for custom color maps and fixes to the raster driver and the MySQL database driver
Changes
* You can now conveniently include your custom color maps in an `EXTRA_CMAP_FOLDER` of your choosing, thanks to dionhaefner
* Rasters with existing alpha bands now just work (176) fixed by dionhaefner
* `/colormap` response changed: JSON key is called `rgba` instead of `rgb` and contains 4 values.
Bug fixes
* MySQL database driver getting into broken state limbo is now prevented (174), by j08lue and dionhaefner
Other
* Docs now rst-magically build the color map visualizations and got rid of their Matplotlib dependency, by dionhaefner