Filters as read-only parameter can break the assembly build of a multi-module project

When I specify <build><filters> in the root project for filtering files of an assembly, then running "assembly:assembly" breaks. This is because <build><filters> configuration is inherited in the modules, and Maven does not correctly inherit this configuration (see MNG-2445).

I attached an example project to test this:

• run "assembly:attached" on the root project: it works fine
• run "assembly:assembly" on the root project: it breaks

I think the "filters" argument of the assembly plugin should not be read-only. Instead, it should be possible to redefine it locally, or leave it blank if we want the plugin to take the <build><filters> definition instead.

What do you think of this? I can work on this.