avoid c++'s static initialization order fiasco
GetDataDir(): cache paths for each network separately

Conflicts:
	src/util.cpp
don't relay checkpoints to peers before version negotiation

fixes misbehaviour noise
fix segfault on testnet
command getsubsidy is thread-safe
add new command getstakesubsidy
Add support for watch-only addresses

Changes:
* Add Add/Have WatchOnly methods to CKeyStore, and implementations
  in CBasicKeyStore.
* Add similar methods to CWallet, and support entries for it in
  CWalletDB.
* Make IsMine in script/wallet return a new enum 'isminetype',
  rather than a boolean. This allows distinguishing between
  spendable and unspendable coins.
* Add a field fSpendable to COutput (GetAvailableCoins' return type).
* Mark watchonly coins in listunspent as 'watchonly': true.
* Add 'watchonly' to validateaddress, suppressing script/pubkey/...
  in this case.

Based on a patch by Eric Lombrozo.

Conflicts:
	src/keystore.cpp
	src/keystore.h
	src/rpcclient.cpp
	src/rpcserver.cpp
	src/rpcserver.h
	src/wallet.cpp
	src/wallet.h
qt: Hide unspendable outputs in coin control