Update characters_editor implementation, assets and documentation

manifest.json

@@ -8,9 +8,13 @@
   "sources": [
     "src/**/*.cs"
   ],
+  "test_sources": [
+    "tests/*.cs"
+  ],
   "depends": [
     "tools_base>=1",
     "characters_base>=1",
+    "stats_base>=1",
     "ui_base>=1"
   ],
   "test_suites": [