Drop fees by 10x due to the persistently higher exchange rate.

The last fee drop was by 5x (from 50k satoshis to 10k satoshis)
in the 0.8.2 release which was about 6 months ago.

The current fee is (assuming a $500 exchange rate) about 5 dollar
cents. The new fee after this patch is 0.5 cents.

Miners who prefer the higher fees are obviously still able to
use the command line flags to override this setting. Miners who
choose to create smaller blocks will select the highest-fee paying
transactions anyway.

This would hopefully be the last manual adjustment ever required
before floating fees become normal.
Increase default -blockmaxsize/prioritysize to 750K/50K
Add rpc command 'getunconfirmedbalance' to obtain total unconfirmed balance

Conflicts:
	src/rpcserver.cpp
Fix infinite loop with LogPrint on Windows

Running -printtodebugger -debug (or -debug=lock),
compiled with -DDEBUG_LOCKORDER would infinite loop
on Windows because every critical section lock/unlock
triggers a LogPrint.

Solution is to use the raw boost mutex instead of a CCriticalSection.
Use thread-local storage for LogPrint(category...)

This prevents crashes at shutdown where a global destructor
calls LogPrint(category...) after mapMultiArgs has been
deleted.
[Qt] add messages when handling local payment request files

- important for the open URI dialog to give users feedback
  when a file is invalid etc.
Add tests for correct and incorrect order of signatures for a multisig
(P2SH)
[Qt] fix RecentRequestsTableModel function ambiuguity

- fixes a compiler ambiguity error with ::createIndex() called in
  RecentRequestsTableModel::index()
- also add some Q_UNUSED() macros
Merge src/leveldb changes for LevelDB 1.15
Squashed 'src/leveldb/' changes from 936b461..e991315

e991315 Merge upstream LevelDB 1.15.
0cfb990 Release LevelDB 1.15
02ac9f1 Merge upstream LevelDB 1.14.
0b9a89f Release LevelDB 1.14

git-subtree-dir: src/leveldb
git-subtree-split: e991315d7fe4ca84a98902578106cbffa3dcccfd
build: fix detection of boost libs on multi-arch distros

Fixes #3219.
docs: remove workaround instructions now that the problem is fixed
Merge pull request #3407

952fe2e docs: remove workaround instructions now that the problem is fixed (Cory Fields)
efdfee4 build: fix detection of boost libs on multi-arch distros (Cory Fields)
Merge pull request #3326

ad898b4 Increase default -blockmaxsize/prioritysize to 750K/50K (Gavin Andresen)
Merge pull request #3387

3e01c00 Add tests for correct and incorrect order of signatures for a multisig (P2SH) (Tamas Blummer)
Rebrand to `Bitcoin Core`

Only messages for now, executable names and other file names
can be changed later if necessary and safe.

Do not do an all-sweeping change. Some occurences of Bitcoin-Qt need to
be kept:

- Applicationname: this is used to determine the registry entry names,
  we don't want to lose settings over a silly name change.
- Where it refers to the executable name instead of the product name.
update help for -blockmaxsize and blockprioritysize

- was left out in #3326
Merge pull request #3409

a9a37c8 update help for -blockmaxsize and blockprioritysize (Philip Kaufmann)
fixed documetation on hardening flags
Merge pull request #3411

08b93f9 fixed documetation on hardening flags (HaltingState)