ENH: Add NeedleFinder extension

Description:
NeedleFinder: fast interactive needle detection. It is an open source
software for MR-Guided Interstitial Gynecologic Brachytherapy. It
enables on-time processing of the intra-operative MRI data via a DICOM
connection to the scanner followed by a multi-stage registration of CAD
models of the template and the obturator to the patient images. This
allows the virtual placement of interstitial needles during the
intervention, as well as the detection/labeling of needles in MR images

Contributors:
Guillaume Pernelle,  Alireza Mehrtash, Lauren Barber, Nabgha Fahrat, Jan
Egger, Tobias Penzkofer, Sandy Wells, Sam Song, Xiaojun Chen, Yi Gao,
Antonio Damato, Tina Kapur, Akila Viswanathan
Merge pull request #639 from gpernelle/add-NeedleFinder-master

ENH: Add NeedleFinder extension