Add basic incremental level logic

[lloydlobo]

Future

• Add main menu (medium priority)
• Add a better HUD
• Add atmosphere sfx

Commits

• Abstract code from love api into their own functions
• Refactor commons and configurations into own modules
• Tidy up code into sections
• Stream background music and add victory and defeat sfx
• Add sfx for laser, healing, victory, defeat etc
• Brighten up player and background colors, to go with upbeat bgm
• Add game level counter WIP
• Automatically bump game_level and simultaneously increase initial creatures
• Add release make command