Bind goto_line function for Script Editor

[mawenzy]

Bugsquad edit: Fix #9153

[Chaosus]

Thanks for the contribution, please squash the commits together, see http://docs.godotengine.org/en/latest/community/contributing/pr_workflow.html#mastering-the-pr-workflow-the-rebase

[toger5]

separating the docs into other commits makes sense though. especially the doctool update?

[akien-mga]

Thanks!