I just reviewed. For the 1st time, a start component review was (almost) straightforward, with useful comments and all. I remember how I was lost the 1st time I naively started to try to understand OFBiz code by reviewing the start class. Kudos, this was not an easy task!
All works as expected (including the tests and the pos and both options)
I agree with Jacopo's recommendations, I'd maybe just add a comment about the ofbiz.admin.port use in the tops of the classes. This port and its usage are quite important, so better let's new users not miss it.
Not sure why you removed commandExistsInList(), found it was more readeable before.
I'd remove the "StartupControlPanel." prefixes in StartupControlPanel class
Ah, I just found this line at the end of a tests run or quitting from the POS using the both option
[java] 2016-06-07 08:57:03,743 FATAL Unable to register shutdown hook because JVM is shutting down.
but I don't think we should mind since after all the tests and the POS work as expected
I also noticed something: you can't stop the backend (not POS part) using "ant stop" when you start with "ant start-both" (this was working before, see R15.12), you get
[java] Start.java using configuration file org/ofbiz/base/start/start.properties
[java] Set OFBIZ_HOME to - C:/projectASF-Mars/ofbiz
[java] Shutting down server : FAIL
Total time: 1 second
But you can still quit all using the POS, which is fine with me.