A patch to improve modding and fix some bugs

• Fixed issues with dual pads: both going to the same place and secondary not hiding during pause.
• Added config options for display name, save file names.
• Improved errors when an invalid path is to be loaded.
• Map tunnels are included in the free play preview. However, it might cause black lines under anti-alias.
• Readme/manual has been rewritten into an HTML document that can be opened using a web browser. Fixed wording and themed a bit.
• Fixed a crash that occurs when the hole has no small lights.
• Exiting a map mid-level no longer saves the entire data into a .dat file, as this method of save/load was quickly replaced.
• In order for the orb not to be shot while pressing on Menu button, there was previously a hard limit for the mouse cursor under which orbs cannot be shot. Now it simply checks that the Menu button is not being hovered over.
• Powerups no longer tend to drop towards the bottom when the rotating shooter is in use.
• Improved shot orb collision detection. It now checks for distance between it and other orbs or powerups instead of overlapping images.
• Fixed Electric Beam simply removing the orbs and not adding points. It, Fireball and Colour Bomb now also display the amount of points received. Also fixed Electric Beam and Accuracy positioning.
• Fixed orbs not resetting when shot from the pad towards the bottom.
• Endless level system takes the amount of available difficulties into account.
• Improved secondary colours. Colours the shooter does not have a sprite for should now be available.
• Made Poison and Inferno less prone to throwing errors.