Updates for MRtrix3 3.0_RC2

[Lestropie]

• Modify dockerfile to pull the 3.0_RC2 tag.

• Use mrdegibbs rather than unring.a64.

• Use mtnormalise, including accounting for the scaling factor embedded in the image header in group-level analysis. Remove dwiintensitynorm step.

• Consider incorporating upsampling of DWI data (if >= 2.0mm) prior to CSD.

[Lestropie]

Additionally: Incorporate changes relating to command-line interface in 45fbb8f (requires MRtrix3 commit 09c1f21).

@chrisfilo: With the above, I'll have full control over what command-line options are available only when the script is run within a container. Previously we standardised --participant_label, --n_cpus and -v/--version for BIDS Apps; I'm also retaining -d/--debug from the MRtrix3 library, since it produces much more terminal output and makes it a lot easier for me to see what's going wrong if anyone reports an error. Are there any additional command-line options that you are hoping to see standardised for OpenNeuro?

[chrisgorgo]

Great. Whenever you release a new version we'll deploy it on OpenNeuro.

[Lestropie]

Closing since the latest version is based on MRtrix3 version 3.0_RC3. Some elements listed here will go into a new issue instead.