small reorg, some improvements, readme updates

- fix hemtt config to copy example
- add measurements table in Readme
- ENTITY COUNTS
  - re add side tags
  - use `side group _x` for units and players
  - fix players_connected and add headless_clients
- get `_allUserInfos = allUsers apply {getUserInfo _x} select {count _x > 0};` from main loop and use in entity counts and player performance

.hemtt/project.toml

@@ -9,7 +9,7 @@ git_hash=6                                # Default: 8
 
 [files]
 include=[
-  "ifxmetrics.config.json",
+  "ifxmetrics.config.example.json",
   "LICENSE",
   "README.md",
   "mod.cpp",