Sort authors additionally to series and series_index (Fix #2001)

Sqlalchemy version2 is now a global flag

cps/constants.py

@@ -20,6 +20,9 @@ from __future__ import division, print_function, unicode_literals
 import sys
 import os
 from collections import namedtuple
+from sqlalchemy import __version__ as sql_version
+
+sqlalchemy_version2 = ([int(x) for x in sql_version.split('.')] >= [2,0,0])
 
 # if installed via pip this variable is set to true (empty file with name .HOMEDIR present)
 HOME_CONFIG = os.path.isfile(os.path.join(os.path.dirname(os.path.abspath(__file__)), '.HOMEDIR'))