Regular Update V1.37: performance improvements and bug fixes

Regular update V1.37

• Resolved the issue that the framerate drops severely in the menu view when all sets are unlocked.

• The hint system for variants and combinational variants with
  should be much faster for larger boards now (thanks to xxuurruuii for suggesting the optimization)

• Fixed several issues in the game credits (thanks to Fermata4)

• Fixed a bug that pressing enter during a pop-up message sometimes crashes the game