CS fixes
Removed unused imports
minor #12837 [2.3] CS Fixes And Removed Unused Imports (GrahamCampbell)

This PR was merged into the 2.3 branch.

Discussion
----------

[2.3] CS Fixes And Removed Unused Imports

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | N/A

##### This pull request fixes some cs issues in symfony 2.3.

As far as I understand, symfony's coding standards dictate that there should be no blank lines between imports and imports should not be prefixed with a slash. There are one or two other tiny fixes in here too.

Also, we should only import things that we actually *use*. :)

Commits
-------

0e4f0e7 Removed unused imports
0fc3369 CS fixes