Updates our code to use the Symfony coding style

Replaces the default value for 5 rules:

• concat_space In the Symfony standard all spacing around the concat (.) operator is removed. I believe this just makes the code much less readable
• phpdoc_separation This is just modified so that it won't insert blank lines between Given, When and Then annotations
• global_namespace_import Symfony does not use imports for Classes and functions in the global namespace (for example it will use \DateTime instead of adding a use DateTime; statement). I think this goes against what we have been enforcing in our project
• single_line_throw With the Symfony setting all throw statements use a single line but if we do this we end with some very long lines
• yoda_style Symfony uses yoda comparisons but in these days of static analysers this is no longer really useful and it just makes the code more unreadable

Please let me know if you disagree with any of these exceptions to the Symfony standard

There are a huge number of files changed. As in previous CS pull requests I have separated the changes in different commits with logically related rules to make this easier to review. Some of these commits are themselves quite big even if they result from the application of a single rule, but in those the changes will be all very similar so I am hoping they will be easy to review. Let me know if you would prefer me to split these large commits into smaller ones.

As in other CS pull requests, once everyone is OK with the changes, I will add another commit with the git blame ignore list of commits that need to be ignored