Interrupting import with Ctrl-C could cause database corruption
because the signal wasn't handled. utils.ImportChain now checks
for a queued interrupt on every batch.

The renaming should make it clearer that these functions create a new
instance for every call. @obscuren suggested this renaming a while ago.

The blockchain commands don't need the full stack. With this change,
p2p, miner, downloader, etc are no longer started for blockchain
operations.

eth: hard disconnect if a peer is flaky

ethdb, common: cache removal

cmd/geth: expand admin.progress() to something meaningful

Miner time fix

cmd/geth: exit the console cleanly when interrupted

Update ValidateHeader comments

* Miner should no longer generate blocks with a time stamp less or equal
than it's parent.
* Future blocks are no longer processed and queued directly.
  Closes #1118

miner: log locally mined blocks after they are 5-deep in the chain

Revert "core: block.gasLimit - parent.gasLimit <= parent.gasLimit / G…

This reverts commit be2b0501.

if you track stale blocks, then you quickly overflow your ring buffer in the local network case where you're mining every block and generating a lot of stales.

core: block.gasLimit - parent.gasLimit <= parent.gasLimit / GasLimitB…

core: block database version update

This fix applies mostly to unsupported terminals that do not trigger the
special interrupt handling in liner. Supported terminals were covered
because liner.Prompt returns an error if Ctrl-C is pressed.

Fine tune seeder and p2p peer handling