Removed completed TODOs.

DG_Approximation.py

@@ -22,17 +22,6 @@ TODO: Discuss referencing info on SSPRK3
 TODO: Discuss name for quadrature mesh (now: grid)
 
 Urgent:
-TODO: Added sign change in stiffness and boundary matrix to accommodate
-    negative wave speed -> Done
-TODO: Unify print commands (f vs no f) -> Done
-TODO: Add method and error info to Mesh -> Done
-TODO: Add use of discontinuity position to all ICs -> Done
-TODO: Change maximum training degree to 6 -> Done
-TODO: Change minimum training mesh size to 2^5 -> Done
-TODO: Enforce shift to be positive for two-sided Heaviside -> Done
-TODO: Remove option to choose training domain -> Done
-TODO: Fix VisibleDeprecationWarning for ndarray decoding -> Done
-TODO: Give option to select plotting color -> Done
 TODO: Move scripts into separate directory
 TODO: Outsource run commands in SM rules into separate files
 TODO: Move plot_approximation_results() into plotting script