Fix wrong identation for lists
Added a note about configuring several paths under the same namespace
Minor simplification of the XML code
Fixed the case of the headings
Added a comma
Fixed the section about getting services from a command
Fixing comment typo for Doctrine findBy and findOneBy code example
[reference] [constraints] fixed outdated docs for the Collection constraint since Symfony 2.3.
Misc. minor fixes mostly related to formatting issues
Added the suggestions made by the great @WouterJ
Fixed the formating of one table (it now uses proper headers)
Linked the cookbook about DIC scopes
Bootstraped the standards for "Files and Directories"
Fixed some minor formatting issues related to lists
Fixed the formatting of one table headers
Removed a tip inside a sidebar

Adding a tip inside a short sidebar isn't very normal. Moreover
it doesn't look right on the website.
Fixed the indentation of one code block
Fixed more table headers formatting
Fixed the indentation of a bulleted list
Added some suggestions and fixed one minor formatting issue