Add Neuropil_LPS.nrrd templatebrain object

[jefferis]

see https://github.com/VirtualFlyBrain/DrosAdultVNSdomains/blob/master/template/Neuropil_LPS.nrrd. This in theory is the current "best" VNC template at Janelia and has been used for a bunch of registrations. Reference is https://www.biorxiv.org/content/early/2017/04/26/122952

[jefferis]

However there is also this: https://www.biorxiv.org/content/early/2018/07/25/376384

[jefferis]

Apparently still not the latest, from Rob Court

yes and no, Hideo did more straightening on my original so I've used that which is (I assume) the Janelia Female VNC 2018 template

20x_flyVNCtemplate_Female_symmetric_8bit_LPS.nrrd