feature #4449 Added cache_busting to default asset config (GeertDD)

This PR was merged into the 2.5 branch.

Discussion
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Added cache_busting to default asset config

See: symfony/assetic-bundle#119

Commits
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733de39 Added cache_busting to default asset config

Author: weaverryan

reference/configuration/assetic.rst

@@ -48,6 +48,9 @@ Full Default Configuration
 
                 # An array of named filters (e.g. some_filter, some_other_filter)
                 some_filter:                 []
+            workers:
+                cache_busting:
+                    enabled:              false
             twig:
                 functions:
                     # An array of named functions (e.g. some_function, some_other_function)