set up a model for bids-example ds000001

[Remi-Gau]

idea sparked by @jmumford

raw and fmriprep are in the bids example but it has no actual data, so it could allow a lightweight example for play around

https://github.com/bids-standard/bids-examples/tree/master/ds000001-fmriprep

[jdkent]

this is started in #8, I have almost what I want:

• adding derivatives to convolution does not work correctly
• this is my interpretation, so it could use a review
• groupby/filter should likely be moved to edge arguments instead of transformation instructions.

also this is an example of using orthogonalize (which as @jmumford mentioned may not be best practice any longer?), so it may be a good idea to also create a model that does follow better practices?