[cctbxbb] simtbx - Pilatus example available

[James Holton]

Took most of last week, but I finally got it to work. 
tst_nanoBragg_pilatus.py will create a Pilatus-like image, complete with 
bad pixels, window panes, thickness effects, module-to-module 
misalignment and 0.1 deg of phi rotation.  It takes one optional 
argument, which is the image number in a sequence of 3600.  I've 
processed this simulated data set with xia2 and XDS and found the 
anomalous signal has the right sign.

This required some edits and additions to the simTBX code as well as 
FormatCBFMini.as_file() that I think fixed a beam center consistency 
bug.  Now if you dxtbx.load() and FormatCBFMiniPilatus.as_file() you get 
the same beam center in both input and output headers.  I also enhanced 
the header to make it look more like the ones in DIALS regression.  A 
new "SIM.F000" value is now available for marking the "direct beam" on 
the image itself.

I spent most of Friday and all of this morning trying to follow the 
check-in procedure we laid out during the DIALS workshop. Not sure how, 
but it suddenly started working just now.  I believe I have checked in 
this code into the simtbx_sandbox branch of cctbx_project.  Is Jenkins 
looking at this yet?  Is anyone looking at this yet?

-James Holton
MAD Scientist