changed model of arguments to use ForeignKey and integer index and deleted ArgumentOrder
fixed tests to use a ROOT_SYMBOL
overloaded save method to set index of arguments properly
changed add_derivate
Merge remote-tracking branch 'origin/newargs' into newargs
refactoring the factory
Merge remote-tracking branch 'origin/newargs' into newargs
better
Merge remote-tracking branch 'origin/newargs' into newargs
removed some append_argument
new structure
Merge remote-tracking branch 'origin/newargs' into newargs
new add_derivate
fixed updated use of add_derivate and create_argument in test_marking.py
Merge remote-tracking branch 'origin/newargs' into newargs
new structure
Merge remote-tracking branch 'origin/newargs' into newargs
fixed updated use of add_derivate and create_argument in test_helpers.py and removed unnecessary get_arguments_for helper
null=True, blank=True for arguments in derivations
Merge remote-tracking branch 'origin/newargs' into newargs