script: rename token CHILD to ARROW and simplify 'actor_list' rule
scripting: fix typo: "mrs_int" -> "mrs_natural"
runner: add support for new marsyas scripts
scripting: simplify parsing actor declaration (name and type)
scripting: use auto-generated MarSystem names, if unspecified
scripting: scanner: fix typo in parsing boolean values
scripting: apply all controls after network tree is constructed

This allows more control over the order in which controls are applied.
Specifically, it allows controls like "AudioSink/initAudio" to be applied
after flow parameters on which the node depends.
scripting: allow digits after first character of identifiers