Building plugin for both 8.0.x and 8.1 series and 8.1 application bundle with recent e.g progress api changes

Hello,

There is something I coudln't figure out on my own, about the api
changes in NetBeans 8.1 (or maybe bigger question how the versioning is
done)...

We have this plugin: https://github.com/testmycode/tmc-netbeans which
consists of the plugin itself and the application part (which I assume
we use for building the bundled plugin+application installer).

Recently we wanted to start building the bundled application with
NetBeans 8.1 so that our users will get the latest NetBeans. So I
routinely upgraded the plugin project to use NetBeans 8.1 as the
nbplatform. However now the api changes, most notably
org.netbeans.api.progress.nb caused some issues. (We use:
org.netbeans.api.progress.ProgressHandleFactory).

After adding this plugin as dependency, new releases, (plugin updates),
will no longer install to NetBeans 8.0.2 clients as the
org.netbeans.api.progress.nb couldn't be found. Error is something like
this (someone managed to install the update to older netbeans:
https://gist.github.com/jamox/f7644f1164f7527b3c0f#file-gistfile1-txt-L
36-L65 (this specific in in a case when installing the update was
possible, or forced). 

What I've figured out, If I use 8.0.2 as the nbplatform, plugins
installed to 8.1 applications will work due to the compatibility
additions. and ofc also with 8.0.2 as plugins was build using it. 

So the question the wall of text leads to:
How I can generate the bundled application installer for 8.1 but build
the application so that the plugin/update would be installable to older
8.0.x NetBeanses as well.

One solution would be to have separate branches even to have one using
8.0.2 and other using 8.1 - which sounds really tedious and error
prone...

Thanks!