Polycom JSON tweaks - Add VVX 500, corrections for current models.

1. VVX 1500 is not a SoundPoint IP phone, so I removed that part from the name.

2. Corrected the maximum line counts based on the Polycom admin guides.  The conference phones only support one registration, where the 650/670 can do 34 when equipped with three sidecars.

3. The VVX 500 is supported by the 4.0.2 RevB firmware revision currently packaged for "spipm", the split firmware file (3111-44500-001.sip.ld) is even there, so I added a named entry for it.