[Feature] Query for more classes

[fforster]

Is your feature request related to a problem? Please describe.
The ability to query more than one class

Describe the solution you'd like
The ability to do this query:
dataframe = alerce.query_objects(
ra=220,
dec=0,
lastmjd=[nt.mjd-365./2,nt.mjd],
radius=search_radius*3600,
classifier='stamp_classifier',
class_name=['SN','AGN'],
page_size=200
)

This was requested by Alex Kim, from DESC.