Make Tubular Geodesics plugins available through the Updater

[tferr]

Tubular Geodesics (TG) is an incredible extension and the best thing that happened to SNT since its inception. Installation of TG is the single most thing users can do to really improve tracing quality. It seems critical to distribute Tubular Geodesics through an update site, either through the base Java 8 update site, or through the Neuroanatomy update site.

The former is much more demanding since we'll have to abide by the Fiji's contribution Requirements. The latter is much more flexible as there are no really no requirements - just ensuring that we will not break the user installation - as described in Distribution guidelines.

@fethallah, what do you think? Would that be OK for you?

My take would be to use to use the Neuroanatomy site to distribute the binaries and update the TG tutorial accordingly. I am guessing that the instructions on the Tubularity repository are awfully outdated and this will require a lot of legwork. I'm also guessing we'll have to set up a Jenkins job for this, as e.g., I do not have immediate access to a Windows machine.