Methods common to all observers
================================

The observer base type is one of two base types (the other being nobserver)
for objects whose primary purpose to derive outputs from layers (directly or
via other observers) outside of the "natural" computation of that object. 
`observer` is the polling type used for model responses, whereas `nobserver`
is triggered by modification events.

description
-----------

	some_obs description

The description of `some_obs` will include the additional `Stalkee` element.

target
------

	some_obs target stalkee

Set the observed object of `some_obs` to be `stalkee`.

report
------

	some_obs report 

Print the derived string state of the observed object.