Remove konsole colorscheme.

This is now in another repo.
Update kate syntax highlighting using native KDE editor and saner colors.

Also add variants for bash and C/C++.
Remove Rakefile and rewrite installer.

Rakefile was broken (see previous commits). Too lazy to fix;
colors ain't going to change every day.

Moreover, generate "Light" colorscheme from "Dark" on install
by swapping monotone palette colors.