Allow user to force writing out datasets with "inherited" invalid attributes

[fedorov]

Problem (reported by @abmnv and Felix Nensa):

Acquisition context is propagated from the source images DICOM. In the instances where there are attributes that are not conforming to the standard, converter will fail due to failing conformance checks in DCMTK. This is disrupting and confusing to the user (user may not have the capacity or understanding to check the problem, user may be confused as to why converter of derived data enforces this, patching source image data may not be an option due to difficulties in propagating the patched datasets throughout the various infrastructure components).

Solution that we should implement (suggested by @michaelonken):

Another idea would require some work in dcmqi: You could create the
segmentation without imported Patient and Study information and patch
that information manually into the dataset after
DcmSegmentation->write(), thus bypassing the checks.

[fedorov]

related to #212