Add option to disable bbox checking in tractogram loading

[AntoineTheb]

Scoring is often done on poorly constructed tractograms, and phantom tractograms often go outside their bounding boxes. It would be nice to add an option to disable bbox checking when loading tractograms so that all scripts working on tractograms can load problematic tck/trks without having to manually disable bbox checking in the code (and risk pushing it).

[AntoineTheb]

Addressed in #641