owheatmap: Change the default under/overflow colors
owheatmap: Change the default under/overflow colors

By default, use extremes from the color gradient instead of white/black.

cheral/orange3,qPCR4vir/orange3,qPCR4vir/orange3,kwikadi/orange3,qPCR4vir/orange3,marinkaz/orange3,cheral/orange3,qPCR4vir/orange3,qPCR4vir/orange3,kwikadi/orange3,marinkaz/orange3,qPCR4vir/orange3,marinkaz/orange3,kwikadi/orange3,kwikadi/orange3,marinkaz/orange3,cheral/orange3,kwikadi/orange3,cheral/orange3,cheral/orange3,marinkaz/orange3,kwikadi/orange3,marinkaz/orange3,cheral/orange3