Rename to CE-modern, a 1.7.10 port of CE

Position this mod as a port of CE instead of BCx.

- Rename the mod to CE-modern (modid cemodern) and the package to
  net.kanawo.cemodern; the main class is now CEModern.
- Move assets to assets/cemodern and rename the lang key and EMC save
  data to match.
- Describe the mod as a port of CE in the README and mcmod.info.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,6 +1,6 @@
-# BCx-modern
+# CE-modern
 
-Minecraft 1.2.5 時代の BuildCraft × Equivalent Exchange アドオン「BCx」を、Minecraft 1.7.10 (Forge 10.13.4.1614) 向けに移植したものです。
+mod「CE」を Minecraft 1.7.10 (Forge 10.13.4.1614) 向けに移植したものです。
 
 ## 追加要素