Plugins that have the capability flag HWPLUG_CAPS_CONVERT set are called
when Hollywood loads the file the user has passed to the program. The plugin
can then examine the file and if it is in a format that the plugin recognizes,
it can convert the file into a Hollywood script and return this script to Hollywood.
Hollywood will then run the script it has received from the plugin instead of the
file it was originally passed.
This makes it possible to enable Hollywood to open custom file formats. The
Malibu plugin, which makes Hollywood able to open Scala project files,
uses HWPLUG_CAPS_CONVERT for this job for example.