Implement the stage 1 tasks from spec http://docs.moodle.org/dev/Render_library_specification

This is best described on the spec doc - please read it!

Specification: Render library specification
Forum discussion: https://moodle.org/mod/forum/discuss.php?d=261202
Advisory posts in General developers forum and Theme developers forum

Please do not discuss the specification here. We would like all feedback to come through the forums, with everything in one place it will be easier to collate the discussions that go on and to produce the final spec.
This Epic will see the tasks the final specification is broken down into completed.

Note - for organisation, this work is being split into 2 epics, this first one (stage 1) and MDL-45826 (stage 2)