Migrate to 2.0 spec

[Guite]

• Raise version to 2.1.0
• CS fixes
• Basic adaptions for core 1.4.3
  • Add Zikula manifest file
  • Use composer instead of old version class
  • Use link container
  • Use new installer class
• Use $this->extensionApi->getModuleInstanceOrNull as a replacement for ModUtil::available
• Users UI listener
• Migrate to Twig
  • Reimplement Smarty plugins as Twig functions
• New controller classes
  • Create dedicated config controller
  • Migrate Ajax, Form, User, Admin
  • Redistribute actions to topic controllers
• Migrate JS to jQuery
• Migrate blocks
• Todo markers
• Move queries into repository class
• Testing