MELPA packaging

• Installable as package from MELPA
• Minor tweaks to improve packaging

Thanks to @purcell for contributing to this release.

Initial release with indentation and syntax highlighting

• Full indentation support for LCB code, including:
  • good handling of continued lines
  • indentation for all core language block syntax
• Syntax highlighting support:
  • all core language block syntax
  • some core language statements
  • string-based highlighting for user constants and variables