Allow exporting after section removal

[KeremKurban]

For a given morphology , especially with new full brain reconstructions, we need to be able to subsample or edit morphologies. One example is Mouselight morphologies where axons are so wide, its not possible to use it on local circuit building in tools for in-silico circuit building. For that , I edited the morphology and removed the unnecessary regions but current version of neuromorphoviz cannot export the edited morphology, only traslocation of nodes are allowed.

Would be great to have that so we can utilize Allen and Mouselight morphologies