Added default pagination params function
Added default pagination params function

The function takes in limit, offset, and sort
arguments, and it will return the default for
each of these if they are set to None. If they
are not set to None, it just returns the
arguments.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/mongochemserver