Added an instrument setup with filters and gratings to the gmos raw fits object

@mhvk Check this out:

```python
tmp = proj.science[0]
tmp.instrument_setup.grating_tilt
<Quantity 56.817 deg>
tmp.instrument_setup.detector1.spectral_cutoff
<Quantity 1025 nm>
```
This might look like playing around - but I now have all the numbers to calculate nm/pixel and do the cutting properly.