JBIDE-17560 use merged target platforms instead of having dupe content in JBT Central and EA sites; add link to verifyTarget.sh in README

JBIDE-17560 use merged target platforms instead of having dupe content in JBT Central

JBIDE-17560 use merged target platforms instead of having dupe content in JBT Early Access site

JBIDE-17560 simplify: no need for second .target file; also purge commented cruft from earlier attempts to load TP w/ all upstream deps

JBIDE-17560 revert to using jbt*-multiple.target in multiple/ folder and use jbt*-multiple-full.target as generated (merged) filename; fix which artifacts are deployed & multiple2repo'd >> master