- Added 'Clr' ("Clear") button to remove all bodies (with keybindings to 'e' key). This is different than creating a new universe, as clearing keeps current parameters (gravity, g.exp., etc);
- Saving/loading G.Exp from universe files;
- Added spacebar keybinding to follow all bodies (change the reference frame to the center of mass of the universe);
- Added checkbox to enable/disable computation about the system's energy info (as it could affect performace);
- Fixed a few memory leaks.
- Refactoring;