Bone positioning now takes into account its parent's absolute rotation,
and compensates it. That means bones with rotated parents follow exactly
the mouse when dragged, instead of going anywhere except where they should.
Repaired selecting bones with the mouse, and made that the default
(can be switched to keyboard with M key).
The timeline grid size and timestep unit size are now variable,
and can be changed with the U, I, O, P keys or the added UI buttons.
Bone borders and joint points can be displayed with B key.
Removed the ignorebone0 button and related functionality.
Minor cosmetical things.
This commit introduces pointer checks to various functions;
so that entity_* will no longer crash or produce weird results
if passed a Node pointer, etc.
The checks are disabled by default, but can be enabled in
ScriptInterface.cpp.
Fixed possible crashes in a few more functions due to missing NULL-checks.
There was a "feature" in the single Lua state that it would keep globals
intact until the game was quit. That made any globals from mods "leak"
into the game or other mods. Now it resets the Lua state when a mod
is loaded or closed.
