• Add ability to specify kernel companions; i.e. check that if some packages are installed in a
  kernel, they must respect a certain version range. Companions can be specified through user
  settings.
• IEnvironmentManager.getPackageManager() returns always the same Conda.IPackageManager
  otherwise signaling package operations would have been meaningless.
• Request environment list access now whitelist=0 or 1 query arguments. If 1, the environment
  list is filtered to respect KernelSpecManager.whitelist. Default is 0, but it could be modified
  in user settings.
• Small UI tweaks