Add configuration for camera assembly mounted on an MIS module

[jsiegle]

Is your feature request related to a problem? Please describe.
Our ephys rigs include camera assemblies mounted on MIS modules, which may be moved to new angular positions for each recording session. However, an MISModuleConfig can currently only be attached to an EphysAssemblyConfig.

Describe the solution you'd like
Create a configuration object that points to a camera assembly in the instrument JSON, and which also includes an MISModuleConfig.