we need renderers for:
- normal
- cli
- html export
At present the CLI handling is hardcoded, this has to be more flexible to allow easy sending from cron. etc. Also Penny could use it in the new portfolio export....
plan:
1/ constants RENDERER_TARGET_NORMAL, _CLI, ...
2/ new $target=null parameter in $PAGE->get_renderer()
3/ some refactoring in renderer constructors and factories