Add twig classes uses

Switch from Packages to PackageInterface
Add todo about possible debug mode implementation
Fix or extend documentation
Replace some SyntaxError with RuntimeError
Remove prefix usage, we now write to output relative to current
directory or with resolved bundle name
Retrieve output url from package getUrl method before resolving bundle
name
Better capture exception in atomic renaming section
Remove PackNode usage and use upsteam Node, SetNode, Textnode and
AssignNameExpression twig classes
Cleanup