More work on implementing remote protocol

Rework things so that we negotiate buffer pools beforehand and only pass
buffer ids around We can then remove the refcount of buffers, events and
commands.
More work on buffer reuse
Use the node state changes to trigger the next step in the configuration
sequence.
Move most of the client-node to a plugin
Do buffer allocation in the port link.

doc/design.txt

@@ -395,7 +395,7 @@ communication channel
 
    node-update
    port-update
-   state-configure
+   state change CONFIGURE
 
 2) Set formats S->C                   CONFIGURE
 
@@ -409,7 +409,7 @@ communication channel
 3) Buffer requirements update C->S
 
    Update port status
-   state-ready if enough formats are set
+   state change READY if enough formats are set
 
 4) Start S->C                         READY
 
@@ -418,43 +418,39 @@ communication channel
    remove_mem
    add_buffer
    remove_buffer
-   start->streaming
+   command START/PAUSE
 
-5) Pause S->C                         STREAMING
+5) Pause S->C                         PAUSED
 
-   stop-streaming
+   state change STREAMING
+   set-format to NULL -> state change to CONFIGURE
 
-5) data transfer C->S
+5) data transfer C->S                 STREAMING
 
    need-input
    have-output
 
-   add_mem
-   add_buffer
    process_buffer
    reuse_buffer
-   remove_buffer
-   remove_mem
+   state change PAUSED
 
 6) data transfer S->C
 
-   add_mem
-   add_buffer
    process_buffer
    reuse_buffer
-   remove_buffer
-   remove_mem
 
 7) format change C->S
 
    port-update
-   state-configure
+   state change CONFIGURE
 
 8) format change S->C
 
    Send set-format change on ports -> READY if new memory requirements
-                                   -> RUNNING if all ok
+                                   -> PAUSED/STREAMING if all ok
 
-9) format-change to NULL  -> CONFIGURE
+9) format-change to NULL
+
+   state change CONFIGURE
 
 10) ERROR