Name popups *Popup and give scripts, scenes and classes matching names

Every popup is now called *Popup instead of *Window in its file, root node,
node name, class and variable, and PopupWindow becomes BasePopup. Player is
PlayerRow, SongListObject is SongRow and Character is CharacterCard. Script
files are snake_case and scene files PascalCase, each matching its class or
root node, and LightGrayTheme.tres is light_gray_theme.tres.

character_card.gd

@@ -0,0 +1,47 @@
+class_name CharacterCard
+extends Control
+
+@onready
+var panel: Panel = $Panel
+
+@onready
+var character_image: TextureRect = %CharacterTextureRect
+
+@onready
+var character_name_label: Label = %CharacterName
+
+signal new_character_selected(img_texture: ImageTexture)
+
+func set_character_name(character_name: String) -> void:
+	panel.size = Vector2(240, 145)
+	#margin.size = Vector2(240, 145)
+	#margin set margin 15, 10, 15, 0
+	character_name_label.text = character_name.split(".")[0]
+	character_name_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
+	var image_fetched: Callable = func image_fetched(image: PackedByteArray) -> void:
+		var img: Image = Image.new()
+		var err: Error = img.load_png_from_buffer(image)
+		if err != OK:
+			GameLog.debug("Character image is not a PNG, trying JPG: ", error_string(err))
+			var err2: Error = img.load_jpg_from_buffer(image)
+			if err2 != OK:
+				GameLog.warning("Could not load the image for ", character_name, ": ",
+						error_string(err2))
+		var new_image: ImageTexture = ImageTexture.new()
+		new_image.set_image(img)
+		character_image.custom_minimum_size = Vector2(200, 100)
+		character_image.size = Vector2(200, 100)
+		character_image.size_flags_horizontal = Control.SIZE_SHRINK_CENTER
+		character_image.size_flags_vertical = Control.SIZE_SHRINK_CENTER
+		character_image.expand_mode = TextureRect.EXPAND_FIT_WIDTH_PROPORTIONAL
+		character_image.stretch_mode = TextureRect.STRETCH_KEEP_ASPECT_CENTERED
+		character_image.texture = new_image
+	MusicServerClient.fetch_character_image(character_name, image_fetched)
+
+func _input(event: InputEvent) -> void:
+	if self.visible == true && Settings.character_select_open == true:
+		if event is InputEventMouseButton && event.is_pressed() && event.get_button_index() == MOUSE_BUTTON_LEFT:
+			var evLocal: InputEvent = make_input_local(event)
+			if Rect2(Vector2(0, 0), panel.size).has_point(evLocal.position):
+				GameLog.debug(character_name_label.text)
+				new_character_selected.emit(character_image.texture)