Update book/forms.rst

Fix typo (missing ";") in source code sample for dynamic validation groups
Added some standards
fix bash command display in components/console/usage
Creates Expression Language chapter
Bootstraps intro
Added operators
Added another operator
Update typo in use_empty_data.rst
Fixed typo in direct_submit.rst
[OptionsResolver] Fix syntax errors in code examples (missing in_array closing slashes)

This pull request fixes 2 syntax errors when using `in_array()` in conditions (missing the last closing slash).

It also adds a missing `use` statement in one code example.
Fix typo
make target name unique that is used as a reference
remove wrong notice on locales in the session, add reference to the relevant cookbook article instead
Merge pull request #3040 from globin/2.3

fix bash command display in components/console/usage
fixed missing syntax highlight on a table name.
Changed slash to backslash in use statement.
Fixed invalid HTML

The <script> tag is not allowed to be self-closing.
Improved code example about memory spooling
widget anchor fixed
minor typo fix