v0.7.0

Features

• Add a ScanVars class for the legacy scan pvs tie-in.
• Automatically load all cameras defined in the camviewer config file.
• Add the --exp arg for forcing the active experiment for the duration
  of a session.

Bugfixes

• Exclude having a beampath when there are no devices on the path.
  This is because the resulting empty path causes issues in the
  environment. This will most commonly occur when calling
  hutch-python with no arguments.