Remove author, updates, and license from file headers.

[DEL] Remove author, updates, and license from file headers.
Clean up the code and redesign game structures.

[NEW] Use version number to limit the version of love engine.
[MOD] Use custom love.run to execute the game.
[DEL] Remove nexus.game and move the functions to main.lua.
[DEL] Remove src/game.lua file.

NOTICE: This version is not playable!
Clean up nexus.core.audio and nexus.core.data code.

[MOD] Move nexus.core.database to nexus.core.data.
[MOD] Rename data/databases/color.lua to data/databases/colors.lua.

NOTICE: This version is not playable!
Complete rewritting nexus.core.input.

[MOD] Rewrite nexus.core.input.
[MOD] Modify the declarations of modules.
Complete rewritting nexus.core.resource.

[MOD] Complete rewritting nexus.core.resource.
Complete rewritting nexus.core.graphics module.

[MOD] Complete rewritting nexus.core.graphics module.
Complete rewritting core modules.

[MOD] Complete rewritting core modules.
Complete refactoring.