v0.4.6: server config for auto-preload on join

- new: config/video_player.json on first server start. Field preload_urls
  is a list of HTTP(S) URLs (≤256 chars each) that the server broadcasts
  via PreloadPayload to every player when they finish joining, so common
  videos are warmed into each client's video_player_cache/ before they
  ever play. Reuses the same PreloadPayload + VideoCache path as
  /videopreload, so chat feedback ("[videopreload] 완료") still applies.
- config is loaded once at mod init; invalid entries are dropped with a
  WARN line. Edit + restart server to apply changes.

gradle.properties

@@ -5,7 +5,7 @@ org.gradle.configuration-cache=false
 
 # Mod
 mod_id=video_player
-mod_version=0.4.5
+mod_version=0.4.6
 maven_group=com.ejclaw.videoplayer
 archives_base_name=video_player