Added new fonctions

Added possibility to change sort field in list mode:
mod.web_list.alternateSortingField.table = field ASC/DESC
Added contentStdWrap to insertLanguagesAndClean function, simply
declare contentStdWrap.xxx in your extension configuration to wrap the
wole content
Added flexFormAutoLoader in Api. Allow to autoload all flexform of an
extension by reading there name and declaring all lines of
ext_tables.php - Thanks Hydris Lefeuvre