Fixed findForward return value, wrapped docs.
Progress on project service.

Now I need to wire up the plugin mechanism by which new project finders will be
exported by packages.
Don't tweak vertical scroll top unless we're way OOB.

Otherwise if you scroll to the bottom, then center the bottom line in the view,
any movement will scroll the bottom line down to the bottom view again. This is
annoying because you put the bottom line in the center of the view on purpose
and obviously want it to stay there.
A whole lotta plugin and project stuff.

- Services can now indicate other services to be injected into their
  construtors.

- Added @Plugin and a mechanism for services to define plugins which can be
  implemented by packages. A service injects the PluginService and then gets a
  reactive set which provides them with a live instance of every implementation
  of their plugin from every package. They can also hear about the addition of
  new plugins (when packages are installed online) and removal of plugins (when
  packages are uninstalled online).

- ProjectService now defines ProjectFinderPlugin which allows a package to
  define a finder for the sort of project(s) it handles. This will allow me to
  create, for example, a scaled-maven-project project which provides a
  specialized Project implementation for Maven projects. &c.

- Other kibbles, bits and gravy bits that I'm surely forgetting.