Update book/forms.rst

Fix typo (missing ";") in source code sample for dynamic validation groups
Update form_collections.rst

The assignment to collectionHolder must be done within jQuery ready function, or else it will be null.
BTW, the variables in JavaScript do not need the $, which is confusing since in jQuery $ has a special meaning.
Fix all lowercase "url" notations to uppercase "URL"
[Reference][Configuration options] Implement consistent headings
Merge pull request #3167 from bicpi/fix_url_notations

Fix all lowercase "url" notations to uppercase "URL"
[Security] fixed a dot in a regex
Merge branch '2.2' of https://github.com/symfony/symfony-docs into 2.2
Collection of fixes: typos, formatting, logic, links
Another collection of fixes: Typos, logic, formatting etc.
updated rexeg
Merge pull request #3169 from bamarni/patch-5

[Security] fixed a dot in a regex
Update form_collections.rst

The variable collectionHolder must be assigned inside the jQuery ready function, but must be declared outside, since it is used also in other functions.

I have put back the '$' in front of names of variables having jQuery objects as values and for uniformity, also added it to collectionHolder.
[Reference][Configuration options] Implement consistent headings standard
Change "swiftmailer" and "Swiftmailer" notation to "Swift Mailer"
Revert notation fix of "DependencyInjection component"
Update validator quoting in Yaml files; add value descriptions; fix spaces
Merge pull request #3157 from attardi/patch-1

Update form_collections.rst
Merge branch '2.0' into 2.1
Merge branch '2.1' into 2.2
[#3157] Removing one extra variable change