Optionally installing Unoconv during initial deployment

[Unoconv](https://docs.moodle.org/33/en/Universal_Office_Converter_(unoconv)) is a command line program that is used to convert between different office document file formats. It uses an instance of LibreOffice to do the conversion and is used by the Assignment activity to convert documents to pdf so that they can be annotated. If unoconv is not installed - the only impact is that the assignment activities will only allow annotations when students upload a pdf document.

How widely used is this? What is the impact if we install it? Can we make it an optional install?

No deployment files, tests, or entry points are identified in the issue. Start by locating the initial deployment entry point and determine how an optional Unoconv installation would affect Assignment annotations; done means the installation choice and its impact are documented and implemented.

Written by the indexing model from the issue text.