Register/Delete robots on web browser

@0ncorhynchus 

Other changes:
- Fix bugs
    - Use 'reason' instead of 'message' as a key
    - Set 'reason'
    - Use urlparse.port 
- Syntax check for some codes using flake8
- Change color of <tr> to show status
- Add 説明書 on the admin page

TODO:
- Enhance UI of admin.html