Restyled and extended Web UI, fixed some bugs

[SiriusED]

Overall:

• +Added: new endpoint /api/clear_table that requires for the Web UI 'Clear data' functionality
• =Changed: db data return structure for better using\reading inside web ui js code

  Web UI:

• =Changed: layout and some styles
• =Reorganized: Web UI files, made them fully portable
• +Added: themes, Light\Dark theme supported
• +Added: buttons to the top panel with new functionality:
  • +Data auto update
  • +Clear all data

    Bugs:

• +Fixed: when user updates landing page ('/') in Web UI, list of the apps duplicates
• +Fixed: static path for the database directory