This PR was merged into the 1.3 branch.

Discussion
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Easier user access

In Silex 1.3, it's "harder" to get the user from the security layer as the `security` service has been deprecated. The code is already available in the security trait, but if you are not using it, you need to use a somewhat "complex" expression in templates to access it (see #1152)

This PR moves the code from the trait to the security service to make it available to everyone.

One question though: can we deprecate the trait `user()` function? It is not useful anymore after this PR.

Commits
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87dc8570 made it easier to get the user from the app