Clean up global datastructures at shutdown.

This should make detecting leaks much easier.
Move GenerateBitcoins() call out of net.cpp's StartNode()

The internal miner is closely bound to the wallet engine,
not the blockchain engine.
Words in English language are more short than in other langs usually.
Tabs don't fits in line in Spanish/German/Russian when they has two words.
Wallet has limited functionality. It can send & receive coins. So we can
safely rename "Send coins" to "Send" and "Receive coins" to "Receive".
Address book is just stored addresses.
Merge pull request #2428 from r000n/staging

Simplify titles of tabs in main window
Bitcoin-Qt: fix copy via context-menu broken

- as QClipboard::Selection isn't available on Windows ensure that the
  correct mode is called, but sill allow selection for e.g. X11
- start conversion from QCoreApplication::instance() to qApp in
  guiutil.cpp (I intend to harmonize this all over the source with my Qt5
  compatibility pull)
translation base files update 2013-04-02

- also includes a small change to a string in bitcoinrpc.cpp, which is not
  on Transifex anyway, so is safe to merge
Merge pull request #2446 from Diapolo/translations

translation base files update 2013-04-02
Merge pull request #2441 from Diapolo/Qt_fix_copy_context_menu

Bitcoin-Qt: fix copy via context-menu broken
Merge pull request #2431 from jgarzik/gen-bitcoins-init

Move GenerateBitcoins() call out of net.cpp's StartNode()
Merge pull request #2420 from sipa/globclean

Global cleanups
Fix signed/unsigned comparison warnings
Shutdown cleanup prep-work

Create a boost::thread_group object at the qt/bitcoind main-loop level
that will hold pointers to all the main-loop threads.

This will replace the vnThreadsRunning[] array.

For testing, ported the BitcoinMiner threads to use its
own boost::thread_group.
Rename util.h Sleep --> MilliSleep

Two reasons for this change:
1. Need to always use boost::thread's sleep, even on Windows, so the
sleeps can be interrupted (prior code used Windows' built-in Sleep).

2. I always forgot what units the old Sleep took.
LoopForever and ThreadTrace helpers
Port Thread* methods to boost::thread_group
Clean up shutdown process
Have Qt poll for shutdown requested, the QT way.