Merge pull request harness#3356 from tphoney/prep2.20.0

(maint) 2.20.0 release prep

Merge pull request harness#3352 from tphoney/prep2.19.0

(maint) prep for v2.19.0

experimental scheduler

Merge pull request harness#3328 from tphoney/v2.18.0_prep

v2.18.0 release prep

release prep for v2.17.0 (harness#3316)

* release prep for v2.17.0

(maint) 2.16.0 release prep (harness#3295)

Merge pull request harness#3281 from harness/prep-v2.15.0

release prep v2.15.0

v2.14.0 release prep (harness#3275)

v2.13.0 release prep (harness#3268)

release prep for v2.12.1 (harness#3232)

* release prep for 2.12.1