Add a -D --define option to set libf3d options directly

[mwestphal]

Is your feature request related to a problem? Please describe.
F3D CLI options are great but being able to set libf3d options directly would provide more flexibility to users.
Being able to reset option would also be great.

Describe the solution you'd like
Add a -D or --define option that would support the following:

./bin/f3d -D=render.effect.ambient_occlusion=true -D=model.scivis.array_name=name

(specific syntax tbd depending on what cxxopts can do)

Also add -R or --reset.

Additional context
#1569

[mwestphal]

related to #1530