add cpt-city selections to distribution

This adds a more complete set of cpt-city gradients to QGis distribution. This is a selection of gradients that can be freely-distributed (according to cpt-city licence files), based on the selections available at the cpt-city web page (http://soliton.vm.bytemark.co.uk/pub/cpt-city/ - Selections from the archive).

This adds about 600 gradients (counting duplicates) and a download size of about 500Kb (compressed).

If the color ramp manager plugin is used, please update the plugin to latest 0.2.2 version and update any gradients, then select "Use gradients that ship with QGis").

With this update, the color ramp manager plugin is not really needed, unless user wants the entire cpt-city collection (around 4000 gradients), or any important updates to the selection are warranted.