Blind duration changes

Changed blind duration range from 3-20 sec to 4-12 sec. Changed the spellpower calculation so that it gets an initial time of 4 sec instead of 5 sec, but changed the final iDuration calculation to range from iDuration-3 to iDuration instead of iDuration/2 to iDuration.

Blind times should be more predictable, but not 100% so.