RFR: JDK-8246627: Consolidate app image bundlers

[Andy Herrick]

Together these two changes might be a lot this late in the cycle, but it 
does make everything cleaner, and passes all test I have tried to run 
with them.

I approve.

/Andy

On 6/4/2020 4:46 PM, Alexey Semenyuk wrote:
> Please review fix [2] for jpackage bug [1].
>
> Move duplicated functionality from LinuxAppBundler, MacAppBundler and 
> WinAppBundler classes in the base class.
>
> [2] webrev is on top of [3] webrev.
>
> - Alexey
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8246627
>
> [2] http://cr.openjdk.java.net/~asemenyuk/8246627/webrev.00
>
> [3] http://cr.openjdk.java.net/~asemenyuk/8246624/webrev.00