xia2 0.2.7.0 released

After a fairly long delay I have put together xia2 0.2.7.0 - this has had a pretty significant amount of testing so should be more solid than previous versions - this is a worthwhile update. Anyhow, here are the changes:

Changes since 0.2.6.6

- All command line options now echoed to the standard output if -debug selected.
- Command line options now copied to .xinfo file when operating in automatic mode.
- XDS: low resolution limit determined from spot list from IDXREF.
- Now include explicit python version check in xia2 main program.
- High resolution limits for integration now assessed from Wilson plot rather than integration program log output.
- If no images are given, a more helpful error message is produced than before, viz:

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| No images assigned for crystal DEFAULT |
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- If images are not readable (i.e. a permissions problem) then warnings will be sent to the debug channel (switch on -debug = for more information.)
- If in automatic mode an image is given in place of a directory, xia2 will now complain in a more helpful way.
- Resolution limits will now be based on analysis of the reflection files rather than the program output, since this will generally give a more helpful answer...
- Now correctly set the reindex matrix for running correct with multiple sweeps of data for non primitive matrix (subtle bug, thanks to Kay Diederichs for helping to fix this one.)
- If images are missing from a sweep, xia2 will now tell you this before starting processing rather than giving a strange error - if the images are unreadable you will also be told.

The biggest fix is the sorting out of resolution limits - you should no longer find xia2 wondering off and then falling over, with ever decreasing resolution limits, in -3d mode. All available from the usual place...