Message buffers allocation

[tcrain]

Allocation of buffers should be handled better.
Currently a message buffer may be copied multiple times after it is loaded from the network,
including when storing to disk.
After a message is read from the network there should be minimal copies.
It should also keep track of if a buffer is read only, so we know when it should be copied.
Also it would be nice to use a pool for message byte buffers to lessen impact of garbage collection.