New Visualizers for the Forces,

added a worldforce option to be based on the output node
Changed the direction of the force arrows to match the force direction
Added better looking icons
Updated Icon of the library
added a libraryinfo.mos so the library can be found in the library selection
Updated QuadraticSpeedDependantForce so that it works properly
updated the pictures of the copyright so that they can be found independant of the working directory
Merge pull request #13 from fvanderlinden/master

Forces visualizers and extra forces