A couple of bugfixes

After yesterdays release I've got some feedback on some annoying bugs that were easily fixable. Here's a list of improvements:

• The block under a teleporter can nog longer be mined and thereby make the teleporter inaccessable.
• Opening any menu does not make you fall at super speed anymore.
• Added a loading screen after pressing Start at the opening screen.
• Greatly improved the FPS by optimizing the code for the blocks.