Add functionality to add "peripherals" to config files

There is a separate location in zookeeper for peripheral files. These files are treated like variables to be injected into an existing file.

Example

```
defaults/
└── open_ephys/
└── config.yml
computers/
└── ...
peripherals
└── treadmill123.yml
```

``config.yml`` gets read like a jinja template. If it contains ``{{treadmill123.yml}}``, the file will look in peripheral for this partial config file and fill it in to the template.

Implementation notes:

- peripheral file names need to be unique (no duplicates)
- need to be able to validate with peripherals (replace jinja variables first)
- determine behavior for if peripheral is missing (return without it? throw an error?) probably the latter