Split the old section on state maintenance into Section 4.4.4 and Section 4.4.5
to avoid confusion between the two types of operation.

Email discussion:

> Section 4.4.3.  At first it seems that to stop the MA from timing out, 
> the Querying node sends another Query.  But later it says that a node 
> can send an MA-HELLO to cause the MA to be retained. Which is it?

This section covers two aspects of state maintenance: routing state and
messaging associations. These are basically independent of each other; the Query
refreshes routing state, and the MA-Hello causes MA keepalive. Would it be
helpful to split 4.4.3 into two parts?

From Lisa Dusseault:

Section 4.4.3.  At first it seems that to stop the MA from timing out, the
Querying node sends another Query.  But later it says that a node can send an
MA-HELLO to cause the MA to be retained. Which is it?