initial addition of pin joint.
anchor rename
pin joint rendering on screen.
Merge branch 'develop' of https://github.com/apportable/SpriteBuilder into chipmunk

Conflicts:
	SpriteBuilder/SpriteBuilder.xcodeproj/project.pbxproj
fix expander.
improve hit test of joints.
working selection, deselections.
Fix observers for Pivots.
Add scene graph instead of Globals.
body nodes can be relocated.
readonly textfield
if physics is disabled, fixup references.
working hidden and visible buttons.
disable physics editor if Join.
Merge branch 'develop' of https://github.com/apportable/SpriteBuilder into chipmunk
add outlets to inspector.
relocating joints works again.
Merge pull request #279 from jtwigg/develop

Develop
Drag and drop beginning to work.
Working drag and drop from joints to bodies.
looking food for drag and drop nodes.