Allow to filter Apps for the PSGI app better:

It used to be possible to create a PSGI app while giving specific
App objects. Now you can also do this using App names and regexes.

This allows one to create a PSGI app as such:

    my $psgi_app = Dancer2->psgi_app( [
        'App1', 'App2', 'App3', qr{^MyCoolApp::Resources}
    ] );
normalize calls to Dancer2->runner->psgi_app as Dancer2->psgi_app
reflect change
update changelog
Merge branch 'feature/filter-apps'