Add fork=true to insight's build (rebased onto develop)



This is the same as gh-1156 but rebased onto develop.

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Under Windows, the error:

 `com.sun.tools.javac.Main is not on the classpath`

can be printed depending on the Java installation.

John Webber (NBI) suggested adding fork=true.

See: http://lists.openmicroscopy.org.uk/pipermail/ome-users/2013-May/003699.html