Much less convoluted way of preventing scrollage when draggage is more apropos.

Also it actually works to the intended effect.
fixed up some encoding nonsense
Freshly added charsheet items now have size_hint_y=1 by default. I'll work on making it adjustable.

EditButton turns out to be pretty fragile, but I think I'll be replacing it with handles for moving items about anyhow.
I never really liked EditButton anyway.

For some reason the StackLayout at charsheet.py:667 is too large with size_hint_y=1. I thought it would only take the available space after the bits with defined heights but no. Then I thought of trying giving the AddButtons size_hint_y of their own, all summing to 1, but that didn't work either, the last AddButton kept running off the bottom. This arrangement works, but I don't understand why.