Change 'AccelerationFactor' to 'ParallelAcquisitionTechnique'

[AdebayoBraimah]

Change AccelerationFactor to ParallelAcquisitionTechnique in the JSON side car. This element should report a string that yields the name of parallel acquisition type (e.g. GRAPPA or SENSE).

The current (float) value that is reported in the AccelerationFactor field should be renamed to ParallelReductionFactorInPlane.

see reference(s) for details:
https://bids-specification.readthedocs.io/en/latest/04-modality-specific-files/01-magnetic-resonance-imaging-data.html
https://github.com/bids-standard/bids-specification/blob/master/src/04-modality-specific-files/01-magnetic-resonance-imaging-data.md

[AdebayoBraimah]

N.B. SENSE is used primarily for Philips - and is currently found by a regex search of the filename and/or certain parts of the PAR header file. Currently unsure if this parameter is report in Philips DICOM header.

[AdebayoBraimah]

Should also add feature that allows for one to specify scanner type - as GRAPPA is the general term.
Vendors have specific names for each of their own parallel acquisition/reconstruction techniques.

see reference for further details:
http://mriquestions.com/senseasset.html

[AdebayoBraimah]

Added the functionality, but it is not accessible. The corresponding fields in the JSON sidecar have been added/updated. These changes will be reflected in the next major release.