Deprecate addRoute-family of functions

[dhil]

The addRoute-family of functions are anti-modular and at odds with the long term goal of moving towards separate compilation. In #938 I briefly made an argument for getting rid of them due to the complexity they impose on the implementation of the webserver and evaluator.

Before deprecating them we should discuss and agree on a modular alternative.

[jamescheney]

+1. Perhaps an alternative could be that the argument to startServer is a list describing the routing table. This would be more restrictive than the current approach in which routes can be added dynamically, but this feature is not used much (and probably shouldn't be).