evil-default-cursor setting should default to the set-cursor-color setting

Originally reported by: **glen_peterson (Bitbucket: [glen_peterson](https://bitbucket.org/glen_peterson), GitHub: Unknown)**

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For those of us who prefer a dark, or black background, a black cursor is unusable. Normally, cursor color is set in .emacs with:
'(set-cursor-color "#ffffff")

With Evil mode, it can only be set with:
'(evil-default-cursor (quote (t "white")))

I'm not the only one confused by this. There are several discussions about setting emacs cursor-color on stack overflow. This question in particular was not solved for 2 years:
http://stackoverflow.com/questions/8204316/cant-change-cursor-color-in-emacsclient/19321267#19321267

It would seem ideal to have evil-mode take the current cursor color setting as its default instead of hard-coding it to white.

Evil mode seems quite nice and the ability to do work by pressing just one key at a time, instead of using emacs chords may make my tendons happy enough to allow me to use Emacs again, which would be a great thing. Thanks for doing Evil!

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- Bitbucket: https://bitbucket.org/lyro/evil/issue/342