Restructure API docs so that they can be formatted with Docbox. (#3355)

Generate Docbox browseable HTML with `npm run build-api-docs`

docs/libosrm.md

@@ -1,7 +1,11 @@
+## Introduction
+
 OSRM can be used as a library (libosrm) via C++ instead of using it through the HTTP interface and `osrm-routed`. This allows for fine-tuning OSRM and has much less overhead. Here is a quick introduction into how to use `libosrm` in the upcoming v5 release.
 
 Take a look at the example code that lives in the [example directory](https://github.com/Project-OSRM/osrm-backend/tree/master/example). Here is all you ever wanted to know about `libosrm`, that is a short description of what the types do and where to find documentation on it:
 
+## Important interface objects
+
 - [`EngineConfig`](https://github.com/Project-OSRM/osrm-backend/blob/master/include/engine/engine_config.hpp) - for initializing an OSRM instance we can configure certain properties and constraints. E.g. the storage config is the base path such as `france.osm.osrm` from which we derive and load `france.osm.osrm.*` auxiliary files. This also lets you set constraints such as the maximum number of locations allowed for specific services.
 
 - [`OSRM`](https://github.com/Project-OSRM/osrm-backend/blob/master/include/osrm/osrm.hpp) - this is the main Routing Machine type with functions such as `Route` and `Table`. You initialize it with a `EngineConfig`. It does all the heavy lifting for you. Each function takes its own parameters, e.g. the `Route` function takes `RouteParameters`, and a out-reference to a JSON result that gets filled. The return value is a `Status`, indicating error or success.
@@ -16,11 +20,14 @@ Take a look at the example code that lives in the [example directory](https://gi
 
 - [Parameters for other services](https://github.com/Project-OSRM/osrm-backend/tree/master/include/engine/api) - here are all other `*Parameters` you need for other Routing Machine services.
 
-- [JSON](https://github.com/Project-OSRM/osrm-backend/blob/master/include/util/json_container.hpp) - this is a sum type resembling JSON. The Routing Machine service functions take a out-ref to a JSON result and fill it accordingly. It is currently implemented using [mapbox/variant](https://github.com/mapbox/variant) which is similar to [Boost.Variant](http://www.boost.org/doc/libs/1_55_0/doc/html/variant.html) (Boost documentation is great). There are two ways to work with this sum type: either provide a visitor that acts on each type on visitation or use the `get` function in case you're sure about the structure. The JSON structure is written down in the [[v5 server API|Server-API-v5,-current]].
+- [JSON](https://github.com/Project-OSRM/osrm-backend/blob/master/include/util/json_container.hpp) - this is a sum type resembling JSON. The Routing Machine service functions take a out-ref to a JSON result and fill it accordingly. It is currently implemented using [mapbox/variant](https://github.com/mapbox/variant) which is similar to [Boost.Variant](http://www.boost.org/doc/libs/1_55_0/doc/html/variant.html). There are two ways to work with this sum type: either provide a visitor that acts on each type on visitation or use the `get` function in case you're sure about the structure. The JSON structure is written down in the [HTTP API](#http-api).
 
-------------------------------------------------------------------------------------------------------------------
+## Example
 
-To summarize:
- - create an `OSRM` instance initialized with a `EngineConfig`
- - call the service function on the `OSRM` object providing service specific `*Parameters`
- - check the return code and use the JSON result
+See [the example folder](https://github.com/Project-OSRM/osrm-backend/tree/master/example) in the OSRM repository.
+
+## Workflow
+
+ - Create an `OSRM` instance initialized with a `EngineConfig`
+ - Call the service function on the `OSRM` object providing service specific `*Parameters`
+ - Check the return code and use the JSON result