LinkedLists for nodes and connections

Connections in nodes are now stored as LinkedLists instead of Lists to
speed up activation and deactivation. The getNodes() cache of DataFile
also uses a LinkedList so that it can be rebuilt more quickly.
Removed generated Library folder from repo
Lockable Toggle

Added a new element to GuiPlus to represent a Toggle that can be
clickable or unclickable. If it is unclickable, the toggle button is
darkened to show it can't be used.
Renamed Connection to Edge

Changed the name of connections to match more closely with the
literature