Add more flexibility in token extractors configuration

[chalasr]

This makes use of the useful canBeDisabled()/canBeEnabled() methods of the Config' ArrayNodeDefinition.

From userland pov, the change is not that big but adds some flexibility.

authorization_header: ~     # array('enabled' => true, 'name' => 'Authorization', 'prefix' => 'Bearer')
authorization_header: true  # array('enabled' => true, ...)
authorization_header: false # array('enabled' => false, ...)

Same for the query_parameter and cookie ones except that they are default disabled (when they are not set at all).