Release v0.10.2

• [FIXED] an error when changing of bus one of the slack (did not trigger the
  recompute of pv bus ids)
• [FIXED] an issue when turning off a generator: it was still declared as "slack"
  if it was one.
• [FIXED] could not disconnect a generator when it was a slack bus
• [FIXED] voltage was -1 instead of 0 for disconnected elements (load, generator, storage units etc.)
• [ADDED] an option in LightSimBackend automatically disconnect load and generators
  if they are not in the main connected component.
• [IMPROVED] refactoring of the c++ side container element to reduce
  code (for "one end" elements such as loads, generators, static generators and shunts)