Multichannel thumbnails use incorrect channel order

For WAV files (at least):

The audioReader does a good job of reading interleaved samples from a WAV file, and rearranging them using the channel order mask from the file, such that the channels all arrive in the correct order as expected by the AudioChannelSet defined in JUCE.

But… the thumbnail cache setSource() method ignores channel order entirely and just stores channel waveforms in the order that they appear in the audio file (which can be a really kooky layout used by nobody anywhere).

Could we please get that channel mapping logic applied when loading thumbnails from file?
Or could you even provide a setSourceFromAudioBuffer() which would avoid the need for double handling?

Two new overloads AudioThumbnail::setSource (const AudioBuffer<float / int>*, ...) has been added.