Adapt collector template name to webprofiler conventions

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | fabpot/Twig#1156
| License       | MIT

Debugging the issue I noticed that the @WebProfiler templates use a different convention.

This is a quick fix.

To allow the conventions most bundles use the Twig_Loader_Filesystem needs to be updated instead.