fix test_dates to chek for RuntimeError on identical date lim test
use the max tick limit for all tick locators
raise if num ticks exceeds some threshold to address sf bug 2715172
testing: add test for bug SF#2715172
Patch artist: emit warning when kwargs conflict (addresses SF#2848629)
testing: remove previous test images, preventing upload of removed tests
removed empty datetime example from test_axes; now in test_dates
testing: fixup failing jpl unit test infrastructure
testing: add missing file
testing: enable test_dates
