saved_progress support for scripted research triggers

[Quezler]

if the trigger for a technology is "scripted" you seem to be unable to set saved_progress on it in order to indicate it to the user, for example when there are multiple entities a player can mine and not just one so you can count it in your script and just update the saved progress and once its ready to hit 100% then you call script_trigger_research() instead.

[protocol_1903]

+1