Added sound management in savegames and load games. (#337)

Fixes #300
Fix crash on loading game when the saved position was a float while teleport_pos command needs integers.
Fix pause menu missing in simplemouse-ui, causing a crash when calling pause menu.
Co-authored-by: StraToN <StraToN@users.noreply.github.com>

addons/escoria-core/game/scenes/sound/bg_sound.gd

@@ -51,3 +51,7 @@ func _ready():
 		ESCObject.new(global_id, self),
 		true
 	)
+
+# Set state to default when finished playing.
+func _on_sound_finished():
+	state = "default"

addons/escoria-core/game/scenes/sound/bg_sound.tscn

@@ -15,3 +15,5 @@ __meta__ = {
 
 [node name="AudioStreamPlayer" type="AudioStreamPlayer" parent="."]
 bus = "SFX"
+
+[connection signal="finished" from="AudioStreamPlayer" to="." method="_on_sound_finished"]