Fixed funky layout (fallout from wx upgrade) in Custom Color dialog
Remove deprecated call to wx.InitAllImageHandlers()
Use default height (indicated by -1) in remaining instances where wx.ComboBox height is init'd to 30.
Refactor long, nearly 100% duplicated splice routines (one called on Splice button click, the other on right-click of "Set" option in splice window) into single method.
Spelling: coeficiant -> coefficient