Add blinking cursor/DOS style cursor support. Related to #136.

Resubmission with things fixed from last request #293.

* changed thin mode color to use text foreground color. Cursor color setting only used in block mode.
* removed the single line that was included by mistake in the last patch.
* rebased to latest master.

I am unable to reproduce the issue of getting the cursor to disappear -- i tried setting unsetting the blink cursor, and hitting apply/cancel, in different order. Can you maybe apply this patch and see if the issue still pops up, and provide more specific steps to reproduce the issue?