Hours to do on chart not over weekends

I forgot to mention that the duration should also not count the weekend in.

(In [11419]) Add resource leveling to scheduler. Refs #9833, #9042, #9290, #9300, #9691, #9784.

This is rather naive. It makes sure a resource isn't doing two things at once but doesn't yet handle priorities when conflicts occur.

(In [11422]) Add task sorter interface. Refs #9833, #9042, #9290, #9300, #9691, #9784.

(In [11423]) Add simple task sorter. Refs #9833, #9042, #9290, #9300, #9691, #9784.

This sorts by Trac's built-in priority field (after converting the priority strings to integers).

(In [11424]) Implement prioritized scheduling. Refs #9833, #9042, #9290, #9300, #9691, #9784.

This is orthogonal to resource leveling. That is even if resource leveling is disabled, this schedules the tasks for a resource using the configured sorting rule.

(In [11426]) A tree-aware task sorter. Refs #9833, #9042, #9290, #9300, #9691, #9784.

A task's priority depends on its parent's priority.

Includes a base sorter class to hold common sorter methods.

SimpleSorter? and ProjectSorter? derive from the base class.

(Copy effective priority list, just in case.)

Also remove unneeded debugging output. Refs #9648.