Update base_layout.html.twig

Before :
![navbug](https://f.cloud.github.com/assets/902990/796902/c4a50be4-ed33-11e2-9776-e59d66db2a7b.png)

After : 
![navbar](https://f.cloud.github.com/assets/902990/796903/cdbaf5a4-ed33-11e2-82ec-e6e8415f8677.png)

Fix navbar alignment of checkbox and button.