Added bg_sound manager and according ESC command.

Started transitions scene.

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

@@ -0,0 +1,42 @@
+extends Control
+class_name ESCBackgroundMusic
+
+func get_class():
+	return "ESCBackgroundMusic"
+
+onready var stream = $AudioStreamPlayer
+var state = "default"
+export var global_id = "bg_music"
+
+
+func game_cleared():
+	set_state("off", true)
+	self.disconnect("tree_exited", escoria.esc_runner, "object_exit_scene")
+	escoria.register_object(self)
+
+
+func set_state(p_state, p_force = false):
+	# If already playing this stream, keep playing, unless p_force
+	if p_state == state and not p_force and stream.is_playing():
+		return
+
+	state = p_state
+
+	# If state is "off"/"default", turn off music
+	if state == "off" or state == "default":
+		stream.stream = null
+		return
+
+	var resource = load(p_state)
+
+	stream.stream = resource
+
+	if stream.stream:
+		resource.set_loop(true)
+		if ProjectSettings.has_setting("escoria/sound/music_volume"):
+			stream.volume_db = ProjectSettings.get_setting("escoria/sound/music_volume")
+		stream.play()
+
+func _ready():
+	escoria.register_object(self)
+

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

@@ -0,0 +1,16 @@
+[gd_scene load_steps=2 format=2]
+
+[ext_resource path="res://addons/escoria-core/game/scenes/sound/bg_music.gd" type="Script" id=1]
+
+[node name="bg_music" type="Control"]
+anchor_right = 1.0
+anchor_bottom = 1.0
+margin_right = -1680.0
+margin_bottom = -1050.0
+mouse_filter = 2
+script = ExtResource( 1 )
+__meta__ = {
+"_edit_use_anchors_": false
+}
+
+[node name="AudioStreamPlayer" type="AudioStreamPlayer" parent="."]

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

@@ -0,0 +1,41 @@
+extends Control
+class_name ESCBackgroundSound
+
+func get_class():
+	return "ESCBackgroundSound"
+
+onready var stream = $AudioStreamPlayer
+var state = "default"
+export var global_id = "bg_sound"
+
+
+func game_cleared():
+	stream.stream = null
+	escoria.register_object(self)
+
+
+func set_state(p_state, p_force = false):
+	# If already playing this stream, keep playing, unless p_force
+	if p_state == state and not p_force and stream.is_playing():
+		return
+
+	state = p_state
+
+	# If state is "off"/"default", turn off music
+	if state == "off" or state == "default":
+		stream.stream = null
+		return
+
+	var resource = load(p_state)
+
+	stream.stream = resource
+
+	if stream.stream:
+		resource.set_loop(false)
+		if ProjectSettings.has_setting("escoria/sound/sound_volume"):
+			stream.volume_db = ProjectSettings.get_setting("escoria/sound/sound_volume")
+		stream.play()
+
+
+func _ready():
+	escoria.register_object(self)

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

@@ -0,0 +1,16 @@
+[gd_scene load_steps=2 format=2]
+
+[ext_resource path="res://addons/escoria-core/game/scenes/sound/bg_sound.gd" type="Script" id=1]
+
+[node name="bg_sound" type="Control"]
+anchor_right = 1.0
+anchor_bottom = 1.0
+margin_right = -1680.0
+margin_bottom = -1050.0
+mouse_filter = 2
+script = ExtResource( 1 )
+__meta__ = {
+"_edit_use_anchors_": false
+}
+
+[node name="AudioStreamPlayer" type="AudioStreamPlayer" parent="."]