UI Nits: Splitter icons adjust

The icons are adjusted via utility function iconFromPNG()
which currently just adjusts the icon color to be a muted
gray as opposed to black.

This is the first pass at recreating the 'template' function
used by the cocoa image functions. Will add an emboss feature
later, but at least now they are less vibrant and when clicked
turn black giving a visual clue that they are clickable.