Update book/forms.rst

Fix typo (missing ";") in source code sample for dynamic validation groups
Added some standards
Creates Expression Language chapter
Bootstraps intro
Added operators
Added another operator
Fixed comments and splitted in intro and syntax
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
Fixed typo

Was:
> This option determines if the form will inherit data fotm its parent form.

Changed to:
> This option determines if the form will inherit data from its parent form.
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
Clarifying some language standards for the docs
[#3149] Tweaks thanks to @WouterJ
[#3149] Tweaking language to use a standard for capitalization