Added stereo presets for cx50 and cx100

[simonarnell]

Closes #180 by adding additional preset files.

I do not have equipment to confirm, but I suspect equaliser parameters may need to be reassessed given the following:

1. The acoustic behaviour of a stereo setup may differ from a mono setup
2. In the case of the CX100 stereo setup, each CX100 speaker's two woofers are wired in parallel per channel (A and B), whilst each speaker's individual tweeters are wired separately to the 30w channels (C and D).

Ideally a maintainer at B&O could confirm when merging.

Screenshots taken from the CX100 mono and stereo upcycle guides for clarity:

CX100 mono

CX100 stereo