Removing Pluto as special case minor planet since it is covered by asteroid...

Removing Pluto as special case minor planet since it is covered by asteroid component. The reason size was not calculated is that its diameter is not available in the JPL data
KStars uses to construct asteroid objects. I hard-coded the diameter now and emailed JPG to fix the issue. Removed most instances where there is a specific selection for pluto since
it should not be treated as such now. Would like to know your input and testing on this as some users might want Pluto to stay as a primary object still. If there is no major objections
then we can go ahead and clean the code for all these direct reference to Pluto include kspluto.h,cpp files. The only exception is in a few places where we need to identify Pluto among
others as a "Minor Planet"

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