Qt: show mined transactions at depth 1

- before, we used to show them in GUI when depth >= 2, which could lead to
  confusion of users, as the RPC behaviour already showed the Tx
remove FIRST_CLASS_MESSAGING support from the client

- removes the FIRST_CLASS_MESSAGING support from the client, which was no
  default setting anyway
Qt: re-order GUI code

- re-order Qt Actions and connect() calls to match the real GUI layout,
  which makes things easier to read and understand
- remove signMessageAction and verifyMessageAction from tabGroup as we
  didn't use them anyway (as tooltips are not displayed in the menu remove
  these too)
- update 2 comments
clear history when using clear button in RPC console

- current code does not clear history, when using the clear button, this
  is added
- remove a currently unused variable but add a TODO comment
check tx.CheckTransaction for data-driven tx tests.

(and change so that only one case has to fail to make a tx_invalid
test correct)
Add various tests for CTransaction::CheckTransaction()
Bugfix: Initialize CWallet::nOrderPosNext on an empty wallet, and save it in db
Add printf-style warnings to strprintf() and OutputDebugStringF()

This finds about ~150 potential problems with format characters on a 64 bit build.
Cleanup some unused macros from util.h

Encapsulate _snprintf/sprintf difference in implementation not header
Improve RPC console key event behaviour

- Paging using PageUp / PageDown now works when entry widget has focus
- Typing or pasting while the messages widget has focus auto-selects entry widget
Cosmetic: move CTransaction::GetMinFee out of header file
Improve debug logging, for mempool TXs that do not include sufficient fees
HexStr: don't build a vector<char> first

Also const correctness for lookup tables in hex functions throughout the code.
Add format characters for (s)size_t and ptrdiff_t
fix signed/unsigned in strprintf and CNetAddr::GetByte()

- I checked every occurance of strprintf() in the code and used %u, where
  unsigned vars are used
- the change to GetByte() was made, as ip is an unsigned char
update comment, secure_allocator is defined in allocators.h
tests for SetCompact and GetCompact of CBigNum
reimplement CBigNum's compact encoding of difficulty targets

Use shifts instead of going through the MPI representation of BIGNUMs.
Be careful to keep the meaning of 0x00800000 as sign bit.
Bump client version to 0.7.0.99 now that 0.7.0 release is final.
Merge branch 'refactor_times' of git://github.com/luke-jr/bitcoin