fix getHex and setHex for ofFloatColor and ofShortColor. closes #1487.
oops. fix getHex for ofShortColor.
make setHex more efficient
use ofColor casting in setHex
use default alpha during conversion in setHex
Merge pull request #1814 from thiagohersan/fix-getHex

fix getHex and setHex for ofFloatColor and ofShortColor