DWIConvert with standard/generic gradient tags

[ihnorton]

DWIConvert currently hard-codes converters for each vendor, but the extraction routine in the Hitachi converter should work for other vendor's data using the "standard" [0018,9087] and [0018,9089] tags (bval and bvec). This could be moved or copied to the Generic converter if those tags are present.

See example Toshiba data on mailing list to which this would apply [1].
(another recent request in [2]).

[1] http://slicer-users.65878.n3.nabble.com/dti-data-dicom-to-nrrd-nii-conversion-td4030790.html
[2] http://slicer-users.65878.n3.nabble.com/Re-How-to-load-Siemens-DWI-data-to-slicer-for-brain-tractography-tp4029882p4030107.html

[ihnorton]

(feel free to assign to me. opening as a reminder for the next time I look at DWIConvert)

[hjmjohnson]

@ihnorton This is a great idea, and it will certainly be easier in the new organization of DWIConvert.

The new location for the common functionality would be in DWIDICOMConverterBase.h class.

There will be more cleanup of this file soon, but I need to get back to analysis of data rather than fixing this code right now.

Hans