scheduler/client: add notion of 'strict memory bound' projects

[davidpanderson]

I recently changed the client so that its estimate of a job's WSS is at least wu.rsc_memory_bound.
This addressed a problem with CPDN apps,
which have small WSS for a while and then get big; the client would run too many of these at once
and when they get big the system would run out of RAM and/or swap.

However, some projects have rsc_memory_bound quite a bit larger than actual WSS,
and this change caused the client to run fewer of these jobs, causing idle CPUs in some cases.

Solution: have a per-project 'strict memory bound' flag, specified in config.xml.
For projects that set this (like CPDN) we'll estimate WSS the new way; otherwise we'll use the old way.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 10.53%. Comparing base (c807354) to head (ceb5113).
Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5669      +/-   ##
============================================
- Coverage     10.53%   10.53%   -0.01%     
  Complexity     1068     1068              
============================================
  Files           279      279              
  Lines         35868    35871       +3     
  Branches       8409     8411       +2     
============================================
  Hits           3780     3780              
- Misses        31694    31697       +3     
  Partials        394      394              

Files	Coverage Δ
sched/sched_config.cpp	0.00% <0.00%> (ø)
sched/sched_types.cpp	0.00% <0.00%> (ø)