More color palettes

[justinlaughlin]

There is a nice resource from Fabio Crameri that provides a lot of color-vision deficiency friendly and perceptually-uniform color maps [see issue 268, and reference]. This PR adds most of those colormaps into GLVis.

Here is an example of batlow

I wrote a small script to help munge the colormap files into something copy-pasteable. I'm not sure if it's worth adding to the repo but I posted it as a gist. The colormaps added in this PR are listed in the gist:

cmnames = ['batlow', 'batlowW', 'batlowK', 'glasgow', 'lipari', 'navia', # continuous
           'oleron', 'bukavu', 'fes', # multi-sequential
           'hawaii', 'buda', 'imola', # discrete
           'oslo', 'nuuk', 'lajolla', 'bamako', 'davos', # categorical
           'bilbao', 'lapaz', 'acton', 'turku', 'tokyo',
           'broc', 'cork', 'vik', 'lisbon', 'tofino', 'berlin', # diverging
           ]