Slate HUD

First release.

• The game's HUD in Slate's look while the Slate style is on: the hotbar, health, armour, hunger, air, a mount's health and jump, experience, the status effects and the held item's name, each where the game has it.
• Every part has a switch of its own, and there is one for the whole HUD (Options > Interface > HUD with Slate Config). A part that is off is drawn by the game.
• A part another mod draws itself is left to that mod: Better Inventory's hotbar, the hearts of Overflowing Bars, Colorful Hearts and Classic Bar.

Slate modules need the Slate Core of their own version: update all of them together.