Kolibri Module routing & plugin conventions

[MCGallaspy]

Based on discussion we decided:

• Django should inject both the portion of the url it captured for routing and the remaining portion which should be routed by the js app.
• We will remove the urls module from plugins -- plugins should only define one url, and we can entirely construct it from the existing plugin attributes for urls.

[benjaoming]

@indirectlylit hope it's okay to assign you this one since you were very active in the discussion from which the decision formed :)

[indirectlylit]

Still unresolved because it turned out to be more subtle than just lists of names and URLs.

Migrating to trello because it needs design & planning: https://trello.com/c/qIy4GgTa/318-core-api-pluggable-routing-nav-bar-items