Oops, I forgot to add one other important comment: The new config parameters should be documented in the fair scheduler's Forrest documentation in src/docs/src/documentation/content/xdocs/fair_scheduler.xml (in the Allocation File section). Also, the documentation should say what happens if the maxTasks of a pool is set lower than its minTasks: in this case, the maxTasks takes precedence. It might also be good to print a warning in PoolManager when loading a config file if we see a pool with maxTasks < minTasks. You should do this after you finish reading the a <pool> element.
One other very minor thing - there seem to be some tabs in the patch, replace them with spaces.
Thanks for taking the time to port this to trunk!