Basic quest system added

Refactor GrowthStats out of CharacterStats

set initial animation for PawnAnim

Just like BattlerAnim before it, we have pawns that are reusable character
controllers, that apply to NPCs and to the playable character. And these pawns
could be any character in the game, so we need to be able to change the skin on
them.

Having separate scenes for animation is also essential for animators to be able
to do their job properly, while the devs can keep working on the Pawn scenes

Also added variables to store references to nodes like AnimationPlayer,
Added Robi sprite, #93

Add physics layers, remove boolean variable to check if the character is
interacting, now the game pauses during interactions
Now using physics layers and masks as well to only interact with the player's
pawn.

This relies on pausing the game: The NPCs still process during pause, as
e.g. if they were walking around you may not want to freeze the entire
game.

The PawnLeader stops as it inherits its pause mode from LocalMap and
GameBoard.

The StartCombatAction unpauses the game to play combat. I've changed the
interaction with map actions so they use the "finished" signal instead
of InteractivePawn waiting for the method to return.

/!\ Nodes you add to on instanced scenes (interactive pawns in this case) are lost when you rename a parent!

Fix a bug that causes skills to be learned at the wrong level.

closes #95

Fix clipping when the `highlight` animation of a `CombatPortrait` sta…

Now, the only animation that modifies the modulate property is `disable`.

Add missing .import files for the turn order interface (close #138)

* Game over screen added

When the whole party is defeated, a game over screen is displayed. The player can either restart the encounter, or exit the game from it.

Closes #29

* Fixed mistakes and removed Game Over scene from CombatArena

* Removed grab focus from selection arrow