Add  parameter for application middlewares (before, after, finish)
feature #1007 Add $app parameter for application middlewares (before, after, finish) (kl3ryk)

This PR was submitted for the master branch but it was merged into the 1.2 branch instead (closes #1007).

Discussion
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Add $app parameter for application middlewares (before, after, finish)

There is small inconsistence between route and application middlewares.

Route middlewares (http://silex.sensiolabs.org/doc/middlewares.html#route-middlewares) can have $app parameter, but application middlewares (http://silex.sensiolabs.org/doc/middlewares.html#application-middlewares) has this parameter missing.

Commits
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38a3c46 Add  parameter for application middlewares (before, after, finish)