Adds viewserver and viewservermanager with docs

ViewServerManager is the class we used to wrap control of the ViewServer (not sure who wrote it originally). I swapped out the reference to `BuildConfig.DEBUG` with a public static field `ON` as in `StrictModeManager`.

The ViewServer class is as it has been passed along through projects; I just cleaned up variable naming, and extracted two of the classes so the size was more manageable; the extraction doesn't offer any further value though, so I can put them back into ViewServer if wanted.

Adding this to NoTils will make it less annoying to add it to a project I suppose; it should therefore reduce any need/desire to do it at an early stage, and so promote yagni.