fixed indentation of docstring
Spec.Query retrieves header, also get slit width for SpeX data

Spectrum Query optionally retrieves the header from the database,
returns it if return_header=True.

BrownDwarf.get_low() adds an astropy unit quantity that is the
slit width in arcseconds to the self.specs['low'] dictionary
(key is 'slit_width') - the header itself is not saved