feature #4842 Add meaning of yellow icon for number of queries (XitasoChris)

This PR was submitted for the 2.6 branch but it was merged into the 2.3 branch instead (closes #4842).

Discussion
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Add meaning of yellow icon for number of queries

Some people (me included) have been confused about why the number of queries is sometimes displayed in a yellow color. Added explanation for this.

Number is from https://stackoverflow.com/questions/17859176/what-does-the-yellow-color-warning-icon-mean-in-symfony2-web-profiler

Commits
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5e687b2 changes as suggested by WouterJ in pull request #4842
5ce0f3d Add meaning of yellow icon for number of queries

Author: weaverryan

book/doctrine.rst

@@ -646,6 +646,9 @@ to easily fetch objects based on multiple conditions::
 
     If you click the icon, the profiler will open, showing you the exact
     queries that were made.
+    
+    The icon will turn yellow if there were more than 50 queries on the
+    page, this could indicate that something is not correct.
 
 Updating an Object
 ~~~~~~~~~~~~~~~~~~