Add mlis for observer_helpers and observer_skeleton

[snwoods]

No description provided.

[psafont]

We probably want to add some documentation-comments to the type signatures here

[lindig]

Some functions have multiple string parameters, no labels, and no documentation.

[snwoods]

Some functions have multiple string parameters, no labels, and no documentation.

They are all based on the ObserverAPI module, but that's an RPC interface definition using declare , which I don't think I can label, so I don't know what the best way to do this would be? I could add a documentation string for each function like:
(** Creates an observer

• debug_info
• uuid
• name_label
  ...
  *) ?
  But I don't know how helpful that would be, or if I should just point to other documentations of an Observer e.g. Xapi_observer or ocaml/libs/tracing ? I have also labelled the parameters in Server_impl module below and they are the same parameters.

[psafont]

Documenting them is good, see how parameters are documented in many of the interface files, this one for example: https://github.com/xapi-project/xen-api/blob/master/ocaml/xapi-idl/xen/device_number.mli#L23

[psafont]

This wording is a bit strange, usually what's explained is the expected result in terms of the input, something like:

Suggested change

	(** [create dbg uuid name attributes endpoints enabled] is for when the
	Observer is created. [uuid] is the Observer which has been created and
	the parameters following are the fields the Observer was created with. *)
	(** [create dbg uuid name attributes endpoints enabled] creates an
	Observer with UUID [uuid]. *)