Dials

* Nexus format files: correctly determine number of images in dataset
* Force scan_varying=False during indexing as indexing only uses static models
* dials.spot_counts_per_image: generate joint .json result file unless told not to.
* xia2: fix HDF5 template issue (xia2/xia2219)
* xia2: fix processing of .nxs files if a _master.h5 file is present for the same dataset
* xia2: save integrated reflections to DataFiles directory

* fix build issues on Mac, cctbx/cctbx_project160
* bug fix for h5 files: write template expected by xds

* Correctly identify Timepix detector images
* dials.image_viewer: Fix issues with mask display, 520
* xia2: use correctly capitalized H5ToXds executable instead of H5ToXDS

* support for scan-varying beam models
* dials.discover_better_experimental_model has been renamed to dials.search_beam_position (418)
* fixed crash on Ubuntu 14.04 (513)
* dials.image_viewer will now work with large Nexus files
* errors when reading files should be more informative

* allow splitting output of dials.spot_counts_per_image per metric
* xia2: fix crash with .xinfo non-native file line endings
* xia2: add full DIALS paper reference

* dials.image_viewer: Fix crash with "dxtbx Internal Error" (493)
* dials.stills_process: Validate mask file exists at the start of the program
* xia2: immediately stop when Aimless failed to process data
* xia2: Warn when using XDS with HDF5 files and necessary libraries are missing (xia2/xia2197)
* Fixed support for DLS I03 full CBF images