Disable debug prints in MeshAggregateManager.
Move all subscription posting into LocationUpdatePolicy.

Instead of having the Proximity implementations deal with posting,
have LocationUpdatePolicy manage the process. This way, it can decide
to just directly post, handle requests immediately, etc. -- it can
decide how to handle requests most efficiently.
Handle (un)subscription requests in AlwaysLocationUpdatePolicy more efficiently.

Instead of passing all requests with post(), using the main strand as
an implicit queue, explicitly store requests, handle them quickly if
they reverse a still-waiting earlier request, only post requests for
processing when one isn't already running, and handle them in batches
so there isn't so much overhead to do minor modifications to the
subscription data structures. The tradeoff is that we now do more
checks up front in the query processing thread. However, this should
improve efficiency in one particular case where we block up the main
strand by posting so may tasks that take a long time to process when a
query is first evaluated and all parts of the tree up to the cut need
to be added and immediately removed.
Longer initial RTO and logging.

Make the initial RTO for connections in SST longer by just multiplying
the value. This makes sure the initial value isn't too low an
approximation if the first round trip happens to be very quick due to
low load (both network and CPU). If it remains as low as the initial
value, it will quickly converge anyway.

Also add a couple of logging statements at insane level for experiments.
Fix clearing of GC'd timers.

"Disable" timers when clearing them when the have no references left
because the function itself uses the liveness lock, which then blocks
proper destruction, getting it stuck in an infinite loop.
Fix bad interaction between switching static/dynamic trees and migration.

When we detect that something should move between the static and
dynamic trees, we save a record and process the move on the next
tick. However, it is possible the object will migrate in the meantime,
leaving a record of the switch but no object to operate on. Removing
the record when the object migrates would be ideal, but is a difficult
change to make because of synchronization. Instead, expose a function
in the location service cache to check whether an object still exists
or not and only process the move if the object is still available.

This also adjusts CBRLocationServiceCache to track existence as a
reference count to handle migrations. Because events can come in from
different servers in the "wrong" order (i.e. get replica from server
B where object O has moved to, then get the replica removal from
server A where it moved from), we need to use counts to track whether
we're aware of *any* valid copies of an object since they all share
one record in the location service cache.
Merge remote branch 'origin/master'

Conflicts:
	libspace/plugins/mesh/MeshAggregateManager.cpp
Fix missing start-comment in MeshAggregateManager, probably lost during the merge.