Config Screen post-merge improvements

[Mirsario]

Long-term continuation issue for #40 and #165.

Features

• Add a button to TML's mod configuration screen.
• Support opening the config screen while playing in a world, thus not requiring log-outs.
• Indicate what the default value of each option is.
• Indicate what the authority side of each option is (Host or Client).
• Implement a preset system, allowing people to, for example:
  • Turn off all features;
  • Enable all features;
  • Enable only clientside features (Being able to run the mod on servers that don't have it would be neat);
• Greet new players with a Welcome to Overhaul screen, prompting configuration. If presets are implemented, they would also appear here.
• Customize Overhaul's keybinds inside our configuration screen.
• Add option relationships. For example, Melee.EnableKillingBlows should be grayed out when Melee.EnableBroadswordPowerAttacks is disabled.
• Add a tiny button for opening Config.toml.

Art

• @anodomani Replace or touch-up config category icons (Assets/Textures/UI/Config/**/Category.png).
• Create icons for most config entries (a lot of which are yet to be added).
  • Contributions are very welcome!
  • Images can be edits of screenshots or in-game sprites, but must be clean, be in x1 resolution, and have no background.
  • They are rendered with dynamic outlines and Earthbound-esque background behind them.

Misc.

• Replace the rather awful .ogv video format with something more efficient, such as x264 .mp4. This may require shipping a custom build of ffmpeg, which is a complicated process.
• Use a data file (*.data.hjson) for linking and customizing config icons, so that there's never a need to have duplicate assets.
• Replace fallback "zooming" config icon backgrounds with an actually dynamic Earthbound-esque background shader.