Feature/load otp data

/var/opt/NAME is for variable data belonging to add-on software as defined in [the FHS spec](http://refspecs.linuxfoundation.org/FHS_2.3/fhs-2.3.html#VAROPTVARIABLEDATAFOROPT), and since I put OTP in /opt/otp, I was being consistent.

This is not a huge issue for me though. I'll make the change to the OTP default as you suggest.