Generalize the splat handler, to work for phase 2 (and not just KA topic tree)

Conflicts:
	kalite/main/views.py
show options to go to previous or next exercise
Merge branch 'release-0.11.1' of github.com:learningequality/ka-lite into 305
added missing close tags, reorg'd code to do proper mem-cached reloading
Update prev/next html to show progress, fix small splat hanlder to handle leaf nodes.
Merge pull request #1241 from aronasorman/305

Allow going to previous or next set of exercises