removed deprecated trust_proxy_headers docs
removed docs on PHP parsing in YAML files
updated deprecated usage of flash bags
removed deprecated min/max/minlength/maxlength constraints
updated the way form errors are customized
removed deprecated cookie config options
removed deprecated auto_start setting
removed deprecated charset setting
Merge branch 'deprecated' of github.com:fabpot/symfony-docs into fabpot-deprecated

Conflicts:
	reference/configuration/framework.rst
	reference/constraints/Max.rst
	reference/constraints/Min.rst
[#2344] Backporting some deprecated features which were not reflected yet
Merge branch '2.1' into 2.2
Merge branch '2.2'

Conflicts:
	cookbook/configuration/pdo_session_storage.rst
[#2344] Adding missing link to trusted_proxies
Merge branch '2.0' into 2.1
Merge branch '2.1' into 2.2
Merge branch '2.2'

Conflicts:
	reference/configuration/framework.rst