Update book/forms.rst

Fix typo (missing ";") in source code sample for dynamic validation groups
Added final override section
Fixed embedded references
Some minor fixes
added docs about child forms customization
CS fixes
Add note about PHP 5.3 behaviour and proxies.
Better wording.
[Doc] add link to Varnish website
remove blank line so that the versionadded directive is rendered properly
Merge pull request #2990 from WouterJ/override_validation

Added last missing override section
[#2990] Minor tweaks to new validation overriding instructions
Merge pull request #3037 from xabbuh/fix-versionadded

remove blank line so that the versionadded directive is render properly
Merge branch 'fix_roles' of github.com:WouterJ/symfony-docs into WouterJ-fix_roles

Conflicts:
	book/http_fundamentals.rst
	cookbook/bundles/extension.rst
[#2996] Tweaks to adding spaces for RST formatting throughout the docs

... there were just some extra spaces, some links were on multiple lines (always), which should be corrected, and some tables got misformatted
fix typo and move reference to the appropriate file
Merge pull request #2997 from WouterJ/fix_form_component

Fixes for Form Component chapter
Merge pull request #2998 from youbs/improve_form_customization

added docs about child forms customization
[#2998] Very minor tweaks
Change order of annotations to be the same as the gengerator

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | doctrine
| Fixed tickets |