simplifying controllers by using Symfony Controller shortcuts
minor #1624 simplifying controllers by using Symfony Controller shortcuts (gondo)

This PR was squashed before being merged into the 2.0.x-dev branch (closes #1624).

Discussion
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simplifying controllers by using Symfony Controller shortcuts

now, when all controllers extends Symfony `Controller` class, instead of ContainerAware as it was before, we can use advantage of `Controller`'s functions.
also making sure that `$this->render(...)` syntax is consistent across all controllers

Commits
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7dab23d simplifying controllers by using Symfony Controller shortcuts