GSIP-115: CoverageView support

GSIP-115: CoverageView support
Ok on the DropDown and the definition one (I would comment the code instead of removing it so it can quickly re-activated afterwards. Is it ok?)
The coverage band definition is disabled (you can't edit it) if the CompositionType is "Band Selection". It will contain your rule (something like speed=SQRT(band1^2+band2^2)) once we activate the other CompositionType (formula based)