GLGEasedValue respects min/max in setCurrentValue

I forget why I didn't do this in the first place, I think I had
intended for consumers of this interface to "do the right thing"
but clearly I've changed my mind, and I think it's more correct
to enforce the minimum and maximum values.

This will be particularly useful for the next commit : controlling
the speed of time. In that case, I really want increment /
decrement with animations, but I'll just be using setValue for convenience.
Add keyboard commands to control the speed of time
Min star size is now 1 pixel

This was causing some weird visual effects when the star was drawn at its
minimum size of 5 pixels, but the scale was such that the habitable
zone for that star would have placed it within the star itself.
Mars should be more brownish red

not magenta
Include names for planets in our solar system
Change how planets are initialized

I want the initializers for the stock "home" planets to
call the init method that was previously called initWithStar
so that we can setup things like trailers and what not. I think
that @andymoe made a good point that it's weird to do a lot
in your initializer, and that having init methods that takes
a lot of parameters is probably an antipattern.