Resolving script test failures for dev / 3.1.0

[Lestropie]

Need to make sure that we run these test explicitly prior to merging 3.1.0 and resolve any outstanding errors.

There's quite a few failures on dev currently.

I've not yet fully investigated the sources of issues, but a few noteworthy ones:

• Precision issues in dwi2response
• Errors in dwifslpreproc arising from dwifslpreproc: -topupfiles option #2150 (should also add some tests for specifically that feature)
• Precision issues in population_template (and concomitantly dwinormalise group)

[Lestropie]

(just confirming that the current script test suite passes on master as at 3.0.4-25-g6ce49cab)