Rebrand as BCx-modern, a 1.7.10 port of BCx

Position this mod as a port of BCx from the Minecraft 1.2.5 era.

- Rename the mod to BCx-modern (modid bcxmodern) and the package to
  net.kanawo.bcxmodern; the main class is now BCxModern and takes its
  version from Tags.VERSION.
- Move assets to assets/bcxmodern and rename the lang key and EMC save
  data to match.
- Fill in mcmod.info (description, author agomizi1cm, credits,
  dependencies) and the LICENSE copyright holder.
- Add a README.
- Remove template leftovers: CODEOWNERS, LICENSE-template, the greeting
  Config, template comments, empty event handlers and the commented-out
  NEI dependency.

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

src/main/resources/assets/bcxmodern/lang/en_US.lang

@@ -1,2 +1,2 @@
 tile.emcBuilder.name=EMC Builder
-gui.emcbuilder.stored=EMC: %s
+gui.bcxmodern.stored=EMC: %s

src/main/resources/assets/bcxmodern/lang/ja_JP.lang

@@ -1,2 +1,2 @@
 tile.emcBuilder.name=EMCビルダー
-gui.emcbuilder.stored=EMC: %s
+gui.bcxmodern.stored=EMC: %s