Include more extensive meta data when converting from DICOM to NRRD

[hjmjohnson]

It is desired that meta data about scan collection be maintained in the NRRD headers.

A format for the NRRD KEYS is
DICOM_{DCMCODE1}{DCMCODE2}{UNUSEDOPTIONALHUMANTEXT}:={VALUE}

DICOM_0008_0060_Modality:=MR
DICOM_0008_0070_Manufacturer:=SIEMENS
DICOM_0008_1090_ManufacturerModelName:=TrioTim
DICOM_0018_0022_ScanOptions:=PFP\FS
DICOM_0018_0023_MRAcquisitionType:=2D
DICOM_0018_0080_RepetitionTime:=12000
DICOM_0018_0081_EchoTime:=92
DICOM_0018_0083_NumberOfAverages:=1
DICOM_0018_0087_MagneticFieldStrength:=3
DICOM_0018_1020_SoftwareVersions:=syngo MR B13 4VB13A
DICOM_0018_1314_FlipAngle:=90

[hjmjohnson]

@ihnorton FYI: I addd this feature for the new DWIConvert. I am working through some compiler issues for multiple platforms, but this should be released soon.

[hjmjohnson]

Merged in #315 .