replace int with size_t in stream methods

Thus the read(...) and write(...) methods of all stream classes now have identical parameter lists.
This will bring these classes one step closer to a common interface.
gui: remove redundant numTransactions tracking

This number was still tracked even though it's shown nowhere in the UI
anymore. It was originally removed because it didn't match the actual number of
records in the view (which contains outputs, not transactions) thus was
confusing people.

Conflicts:
	src/qt/walletmodel.cpp
	src/qt/walletmodel.h
Make CScript::clear() release its memory
Add network traffic graph

Conflicts:
	src/bitcoinrpc.cpp
	src/bitcoinrpc.h
	src/net.cpp
	src/qt/Makefile.am
	src/qt/clientmodel.h
	src/rpcnet.cpp
Bitcoin-Qt: never display own block count > estimated block count

- some users reported it as weird, that the estimated block count could be
  lower than our own nodes block number (which is indeed true and not good)
- this pull adds a new default behaviour, which displays our own block
  number as estimated block number, if own >= est. block count
- the pull raises space for nodes block counts in cPeerBlockCounts to 8 to
  be more accurate
- also removes a reduntant setNumBlocks() call in RPCConsole and moves
  initialisation of numBlocksAtStartup in ClientModel, where it belongs
Change progress bar from block-based to time-based

This is less confusing to most people, and doesn't rely on estimates
of the total number of blocks received from other nodes.

Conflicts:
	src/qt/bitcoingui.cpp