add physics
prep for arc intersection drawing
add <g> wrappers to center and arcs
more wrapping

it'll make drawing easier, i swear
add arcs' clip path
Refactoring, Illegal connection prevention

- refactoring
dot->Dot
connection->Connection
- added canTakeInput value to DOT_LIST elements
- if, while making a connection, the destination node has
canTakeInput==false, no connection is made
- The user probably needs to be alerted of why the connection failed
(currently just in JS console)
fixed connection with no destination
Refactoring

arc->Arc
add clippath math
remove logs
remove continuous physics
fix clip path on open/close
fix unneeded global var
fix precision error
move globals to globals.js
add continuous physics toggle global
fix 0 arc causing clip path redraws
merge master into overlap-prevention
fix arcs vanishing on drag
move dot to front on drag