Update to Nsvsys (obs2.py)

[joeskeens]

Hello, I have been working with some RINEX2 data that includes BeiDou satellites, and I ran into a problem in obs2.py:

    data[i, j, isv] = darr[:, k]
IndexError: index 45 is out of bounds for axis 2 with size 36

The issues is caused by the Nsvsys variable, which sets the size of the data's third axis and is set to 36. The BeiDou PRNs currently go up to 62, so I think this hard-coded number needs an update. I changed it to 62 locally, and my issue was resolved.

Joe