app: clean up a lot of werid code in GimpColorOptions and GimpFilterOptions
First of all, derive GimpFilterOptions from GimpColorOptions, not the other way around, which was a sick way of magically showing the right options for various tools. That approach has failed and needed additional hacks to do the right thing. Simply have the right class hierarchy and call the right tool options GUI constructors and done. Remove gimp_histogram_options_gui(), we don't need histogram scale controls in tool options when we already have them next to the histograms in the tool dialogs. Also remove gimp_histogram_options_connect_view() and use a simple g_object_bind_property() instead.
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