axis and label fonts of itom2dqwtplot reset upon change of colormap

[M. Gronle]

If another font is set in the property dialog of an itom2dqwtplot and the color-map button is pressed to select another color map, the font properties are reset to Helvetica, 12.

[Robin Hahn]

fixed #7 : after setting the colorMap it is not necessary to call the refreshStyles()...

→ <<cset 4fe12b2627aa>>