Support a custom list of assessments during the build step that specify the assessments to include

[jessebeach]

Right now, all available assessments are built into Quail during the build step.

We should add the option to include a configuration file that specifies specific assessments to include.

This will result in a smaller Quail build for targeted use-cases.

[jessebeach]

We've got this now with #386 in master.