Add support for Jinja config files in coco

[andrerenard]

We would like to support Jinja (.j2) files in coco to match support added to kotekan.

This should be fairly simple, but we'll have to carefully decide how to deal with include folder locations and external Jinja variables. e.g. if we have a configuration file which can operate in multiple modes (based on optional variables), how does coco set the mode?

This is low priority, but would be nice to reduce the length (and possibly number) of CHIME configs.

[ketiltrout]

We use ansible, which already uses Jinaj2 for templating, to deploy the coco config files.

For CHIME, at least, this doesn't seem like it would be worth the effort: we're going to run Jinga2 at install-time via ansible, and install the resultant conf files, rather than installing j2 files on the server and having coco de-jinga-fy them at runtime.