Doc updates

Documentation/TERMINOLOGY

@@ -1,22 +1,15 @@
-
-_Function_: A _function_ is the smallest unit of a program in Fission.
-It's a program with an function as an entry point -- it doesn't have
-to be just one function.
+_Function_: A fission function is something that's mapped to a
+_trigger_ and run on demand.  Though we call it a "function", this is
+a bit imprecise, since it's actually a module with an function as an
+entry point -- it doesn't have to be just one function.
 
 _Trigger_: Triggers are what cause functions to be called.  For
-example the HTTP trigger causes functions to be called on HTTP
-requests.
+example, an HTTP trigger causes functions to be called on HTTP
+requests.  Kubernetes Watch triggers cause functions to be called when
+a Kubernetes watch changes.  Future triggers will include message
+queues, timers, storage systems, etc.
 
-_Instance_: Fission creates and runs servers containing these
-functions.  The running server is called an _instance_.  You normally
-don't need to worry about instances: their management is completely
-automatic and transparent to you.  However, certain configuration
-settings allow you to tweak the behaviour of instances -- for example,
-you can configure the strategy for destroying unused instances.
-
-_Generic Instance_: An instance with no user code in it.  The process
-of including the user code to a Generic Instance is _Specialization_,
-and the resulting instance is a _Specialized Instance_.
-
-_Specialized Instance_: See _General Instance_.
+_Environments_: Environments are the language-specific parts of
+Fission.  Environment containers wrap the user's function and present
+a common interface to the rest of the fission framework.