Modify module loader to load GuiModule from pipe-module-gui
Move GuiModule into pipe-core and swap from reflections to guava for
dynamic loading #70
Change StateSpaceModule to dispose on close #70 to stop whole app exiting
Remove print message from ModuleManager #70
Fix problem with cyclic edges

* jpowergraph considers edges to be equal if the from = to and vice
  versa, this was leading it to believe back edges were already
  contained

* Create own edge type and everything works well