Add additional speaker setups to DirectSpeakers plugin

[rsjbailey]

For the monitoring plugins it makes sense to limit ourselves to the setups in BS.2051, but I realised, that this does not really make sense for the DirectSpeakers plugin. It is reasonable to assume, that one e.g. might also want to add a 5.0 source to a mix.
Does it make sense to allow all the setups which are defined in the common definitions?

(comment)
I think so. You're never going to get complaints that you support too many speaker layouts :) but you might if someone tries to import an ADM file with a common def directspeakers pack that isn't supported.

I allow all in the ADM Export VST, simply because they may be useful and it's no extra effort to include them. In fact, with the way that code works, it would have been more effort to exclude some - I just iterate common def pack formats with the directspeakers type definition and use a simple string manipulation method to make a "friendly" name out of the pack format names.

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