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.

LogPopup.tscn

@@ -0,0 +1,47 @@
+[gd_scene load_steps=2 format=3 uid="uid://bijh5h5yrivm3"]
+
+[ext_resource type="Script" uid="uid://cw41y87l64qo7" path="res://log_popup.gd" id="1_q72ua"]
+[ext_resource type="Theme" path="res://popup_theme.tres" id="popup_theme"]
+
+[node name="LogPopup" type="Control" node_paths=PackedStringArray("panel")]
+theme = ExtResource("popup_theme")
+custom_minimum_size = Vector2(700, 700)
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1_q72ua")
+panel = NodePath("LogPanel")
+
+[node name="LogPanel" type="Panel" parent="."]
+unique_name_in_owner = true
+visibility_layer = 513
+custom_minimum_size = Vector2(700, 700)
+layout_mode = 0
+offset_right = 700.0
+offset_bottom = 700.0
+
+[node name="TitleLabel" type="Label" parent="LogPanel"]
+layout_mode = 0
+offset_top = 8.0
+offset_right = 700.0
+offset_bottom = 48.0
+theme_override_font_sizes/font_size = 25
+text = "Log"
+horizontal_alignment = 1
+
+[node name="LogScrollContainer" type="ScrollContainer" parent="LogPanel"]
+layout_mode = 0
+offset_left = 20.0
+offset_top = 56.0
+offset_right = 680.0
+offset_bottom = 684.0
+horizontal_scroll_mode = 0
+
+[node name="LogVBoxContainer" type="VBoxContainer" parent="LogPanel/LogScrollContainer"]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+theme_override_constants/separation = 1