Add dumpwallet and importwallet RPC commands

fix makefiles and init.cpp after chainparams merge

- add missing chainparams.o to some makefiles
- remove a double-include of chainparams.h in init.cpp

init.cpp: fix chainparams.h double include.

Noticed by Diapolo.

RPC: add 'verifychain' to verify chain database at runtime

Refactor fee rules to make them actually readable.

recognize Debian kFreeBSD port by build_detect_platform script

Update HomeBrew makefile patch

dumpwallet: produce a dump of all keys in a wallet, in a format
compatible with Bitcoin Wallet for Android and Multibit.

importwallet: import such a dump

Compute safe lower bounds on the birth times of all wallet keys. For
pool keys or keys with metadata, the actually stored birth time is
used. For all others, the birth times are inferred from the wallet
transactions.

This function finds all keys affected by a particular output script,
supporting everything ExtractDestinations supports (pay-to-pubkey,
pay-to-pubkeyhash, multisig) and recurses into subscripts (P2SH).

Refactor chain-specific tweaks into a CChainParams class and introduce a regtest mode

Refactor keytime/metadata and wallet encryption bugfix

Refactor keytime:
* Key metadata is kept in a CWallet::mapKeyMetadata (std::map<CKeyId,CKeyMetadata>).
* When generating a new key, time is put in that map, and new key is written.
* AddKeyPubKey and AddCryptedKey do not take a creation time argument, but instead
  pull it from that map, if it exists there.

Bugfix:
* AddKeyPubKey and AddCryptedKey in CWallet didn't override the CKeyStore
  definition anymore. This is fixed, as they no longed need the nCreationTime
  argument now.

Also a few related other changes:
* Metadata can be overwritten.
* Only GenerateNewKey calls GetTime(), as it's the only place where we know for
  sure a key was not constructed earlier.
* When the nTimeFirstKey is known to be inaccurate, it is set to the value 1
  (instead of 0, which would mean unknown).
* Use CPubKey instead of std::vector<unsigned char> where possible.

The new class is accessed via the Params() method and holds
most things that vary between main, test and regtest networks.
The regtest mode has two purposes, one is to run the
bitcoind/bitcoinj comparison tool which compares two separate
implementations of the Bitcoin protocol looking for divergence.

The other is that when run, you get a local node which can mine
a single block instantly, which is highly convenient for testing
apps during development as there's no need to wait 10 minutes for
a block on the testnet.

Move out of main.h to improve compile times and add documentation
for what the methods do.

fix comment about dust logic

Send tx relay flag with version message

allow txindex to be removed and add a reindex dialog

Fix shutdown deadlock, ticket #2690

Remove broken option to skip input checking for wallet txn.

This (nearly) doesn't change fee rules at all:
 * To make it into the fee transaction area, the dPriority comparison
   changed from < to <=
 * We now just ignore transactions > MAX_BLOCK_SIZE/4 instead of
   doing some calculations to require increasingly large fees as
   size increases.

Fixes #2690.

Without this include, sometimes BOOST_VERSION was defined and sometimes
it was not, depending on which includes came before it. The result was a
random mix of sleep or sleep_for for boost versions >= 1.50.

uname -s returns "GNU/kFreeBSD" on Debian GNU/kFreeBSD port. See http://www.debian.org/ports/kfreebsd-gnu/

changes to thread code (directly use boost::thread)

"Wallet birthdays": store key create time; calc whole-wallet birthday

- removes our NewThread() function an replaces remaining calls with
  boost::thread with our TraceThread template
- remove ExitThread() function
- fix THREAD_PRIORITY_ABOVE_NORMAL for non Windows OSes

- adds a reindex dialog for Bitcoin-Qt to change -txindex without the need
  to supply -reindex
- now also does a -reindex, when removing the -txindex switch

Add Linux script to contrib/ that limits outgoing bandwidth to Bitcoin nodes