Removing Single Instance Service from jpackage

[Andy Herrick]

I would like to propose that we remove SingleInstanceService (and the 
--singleton command line option) from jpackage.

The functionality can easily be implemented in pure java, and I no 
longer see the necessity of having it implemented in the launcher. (When 
this functionality was first introduced in the JNLP specification in 
2003, and implemented in Java Web Start, launching java was very 
time-consuming on the hardware available at that time.)

I have created a  simple prototype of a java class "Singleton" that 
implements most of the same functionality in pure java.
(see http://cr.openjdk.java.net/~herrick/Singleton.java)

The prototype has the following public methods start(), stop(), 
running(), and invoke(), and could either be:
a.) implemented by any application requiring this functionality.
b.) added to the JDK for use in any java application
c.) added as a demo or otherwise published by Oracle so it could be 
included as a library in any java applications.

I have created bug to remove this functionality from jpackage 
(https://bugs.openjdk.java.net/browse/JDK-8216190) and am soliciting 
feedback.

/Andy