Instead of 4 zips, merge Central+TP and EA+TP into 2 zips for easier offline use (similar to what we had for JBDS 8)

Today the offline solution [1], [2] for installing stuff from Central or Early Access requires a pair of zips: the 3rd party content (target platform), and the stuff from JBoss Tools.

[1] http://www.jboss.org/products/devstudio/download/ (Central Zip doesn't include the JBT stuff, just the 3rd party / TP content)
[2] https://devstudio.redhat.com/9.0/staging/updates/ (both zips shown)

We should combine these into a single, larger zip, such that the offline solution requires only a single zip and there's no confusion about what a Central Zip is.