Generate a summary reportlet for DWI too

[oesteban]

We are currently missing a summary at the head of the DWI individual report.

In addition to the standard information we plot for BOLD, I'd like to see:

• Number of low-bs/b=0s and whether they are collected together or interspersed and number of DWIs
• Whether it is "shelled" data, single b-value, or DSI as estimated by our NumberOfShells interface.
• Detected shells ("shellified" by NumberOfShells if DSI)

@celprov do you want to take a stab at this?

[oesteban]

More metadata to print out if available:

• Number of volumes per b-value shell.
• RepetitionTime
• EchoTime

[celprov]

RepetitionTime rather than RepetitionType ?