#2461 Issues with run batch and decorators

[Jeremy Faden]

Sadie observed a number of issues with the run batch tool:

1. overlays, like decorators for the polar axes, aren't drawn.
2. the wrong colorbar is used (not greyscale)
3. running individual jobs doesn't write to png.

int generate doesn't appear to work properly with the script testing_stat_microb.jy.

[Jeremy Faden]

I figured this was caused by the decorators not being drawn, but somehow with run batch the decorators aren't there.

[Jeremy Faden]

This was caused by a code change in March which tried to allow for multi-threaded processing with separate doms. This never worked, so the change is reverted.

[Jeremy Faden]

This is fixed.