Improve usage of resource constraint in ListScheduler

There are two unhandled cases that need to be addressed:

1. If the provided amount of resources is lower than the theoretical lower bound the scheduler should not even try, just raise an exception to tell the user.

2. If the user does not provide any resources then -> try lower bound and then go up until success and raise a warning to tell the user what happened.

This will also work nicely when the user is able to specify a scheduling time. (as specified in #292 (closed))