Track partial block download progress, timings and bandwidth, and add disconnect logic for stalls.
Add CaughtUp() function (needed by later commits)
Add extra debugging messages for download and stall logic.
Stripe downloads (so not a contiguous chunk is requested from one node).
Disable sipa stall disconnect logic, but still log when it would have been triggered.
Disconnect no longer useful peers.
Find the runt of the litter (and disconnect it).
Reset variables when network changed.
Allow many blocks to be received in one go from a peer for up to 1 second.

This speeds up IDB.
TEMP logging - show time spent receiving
TEMP logging of nBatch
Debug "block"
Display error when duplicate block received
Request headers while we don't have the headers (fix to headersfirst8)
Improve getheader requests
Improve getheaders (recv) logging
Improve getblocks (reception) logging
Exit UpdateTip earlier so as to give the network a chance to catch up.
Don't disconnect on ping timeout. (Doesn't seem to be a reliable indicator of inactivity).
Improve and shorten "ActiveTip: new best" debug line.