Adds a logic to match NX class at the same level when no base_section…

[sherjeelshabih]

This fixes the issue with voltage_controller/calibration_time in NXiv_temp. Another error shows up with /entry/user/name.

@sanbrock, Lev will have a look into this. When you get time, please check if this makes sense with NeXus inheritance rules generally.

• [ ] Use Florian's NexusTree implementation to generate metainfo