[WebProfilerBundle] Show AJAX requests in the symfony profiler toolbar
feature #12000 [WebProfilerBundle] Show AJAX requests in the symfony profiler toolbar (Burgov, fabpot, stof)

This PR was merged into the 2.6-dev branch.

Discussion
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[WebProfilerBundle] Show AJAX requests in the symfony profiler toolbar

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

Adds AJAX requests in the web debug toolbar.
See #8896 for the original discussion.

![image](https://cloud.githubusercontent.com/assets/47313/4384087/43d1feb2-43b0-11e4-99c9-3e50e19e623f.png)

Commits
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16d1b35 optimized JS for the AJAX section of the toolbar
2e708d7 made minor tweaks to JS code
8e4c603 replaced the AJAX icon with a smaller one
b66f39a removed hack
9c74fcc removed uneeded web_profiler.debug_toolbar.excluded_ajax_paths parameter in the container
d43edaf [WebProfilerBundle] improved the ajax section of the WDT
37f7dd7 [WebProfilerBundle] Show AJAX requests in the symfony profiler toolbar