Improve documentation of wrapSite, runSnaplet and serveSnaplet
Improve documentation of wrapSite, runSnaplet and serveSnaplet

* wrapSite now clarifies that it wraps the base snaplet, not just the current
  snaplet.
* runSnaplet now correctly shows the string "devel", instead of trying to link
  to the `devel` identifier.
* serveSnaplet clearly documents both parameters, providing a hint that
  defaultConfig can be used. Also removed the FIXME comment.

snapframework/snap,sopvop/snap,23Skidoo/snap,bitemyapp/snap