Implement the options menu, part 1

This commit implements loading and saving options from/to config, and
enough UI toolkit magic to allow changes to boolean options to be
persisted.

We now respect the "play movies" setting and take screen resolution
from the config file.

config.toml.example

@@ -1,7 +1,19 @@
 [ordoor]
-data_dir = "./orig"
-video_player = [
-  "mpv",
-  "--no-config", "--keep-open=no", "--force-window=no", "--no-border",
-  "--no-osc", "--fullscreen", "--no-input-default-bindings"
-]
+  data_dir = "./orig"
+  video_player = ["mpv", "--no-config", "--keep-open=no", "--force-window=no", "--no-border", "--no-osc", "--fullscreen", "--no-input-default-bindings"]
+
+[options]
+  play_movies = true
+  animations = true
+  play_music = true
+  combat_voices = true
+  show_grid = false
+  show_paths = false
+  point_saving = false
+  auto_cut_level = false
+  x_resolution = 1280
+  y_resolution = 1024
+  music_volume = 100
+  sfx_volume = 100
+  unit_speed = 100
+  animation_speed = 100