Fix some admin bugs. Non-exhaustive list

• Core
  • Planetary system: Can't access to the PS list.
  • Molecule: Can not add molecules.
  • Planets:
    • Can not create a planet.
    • Can not check if planet have planetary system or star
    • Difficult to choose a star, at least sort the list alphabetically.
  • Publications: Can not create a publication
• Editorial
  • News: Can not create a news.
• FlatePages
  • Can not open flatepage in admin