Added 'immature balance' for miners. Only displayed if the balance is greater than zero.

This adds a field labelled 'Immature' in the overview section under the 'unconfirmed' field, which shows mined
income that has not yet matured (which is currently not displayed anywhere, even though the transactions
exist in the transaction list). To do that I added a 'GetImmatureBalance' method to the wallet, and connected
that through to the GUI as per the 'GetBalance' and 'GetUnconfirmedBalance' methods. I did a small 'no-op'
change to make the code in adjacent functions a little more readable (imo); it was a change I had made in my
repo earlier...but I thought it wouldn't hurt so left it in. Immature balance comes from mined income that is
at least two blocks deep in the chain (same logic as displayed transactions).

My reasoning is:
- as a miner, it's a critical stat I want to see
- as a miner, and taking into account the label 'immature', the uncertainty is pretty clearly implied
- those numbers are already displayed in the transaction list
- this makes the overview numbers add up to what's in the transaction list
- it's not displayed if the immature balance is 0, so won't bother non-miners

I also 'cleaned' the overview UI a little, moving code to the XML and removing HTML.
Make sendrawtx return txid to be consistent with other send methods.
Use ConvertTo to simplify sendmany/addmultisigaddress argument handling
change verifymessagepage behaviour to match RPC-call "verifymessage" (input address, signature and message) / display messages in status label (remove message boxes) / resize window to make signature fully readable / change signature font to BC-address font (like in messagepage) / remove checkAddress() and place code directly in on_verifyMessage_clicked() / add visual feedback to LineEdits / remove AddressTableModel references, as they are now unused / add addr.GetKeyID(keyID) check
move class HelpMessageBox to guiutil.cpp/.h / add button to show Bitcoin command-line options (in RPC Console -> Information) / resize Debug window a little to allow for a non-breaking display of the welcome message with non-english translation
Merge pull request #1364 from Diapolo/move_HelpMessage_GUIUtil_add_RPCCon_Button

GUI: move class HelpMessageBox to guiutil.cpp/.h
Merge pull request #1368 from Diapolo/verifymessagepage

GUI: change verifymessagepage behaviour to match RPC-call "verifymessage"
Merge pull request #837 from sje397/ShowImmatureBalance

Added 'immature balance' for miners. Only displayed if the balance is > 0
Update contrib/debian.

* Updates package description to note that blockchain now takes
  2+ GB instead of 150+ MB.

* Stop creating DB_CONFIG with DB_LOG_AUTO_REMOVE as that is set
  in Bitcoin itself now.

* Update changelog with 0.6.2 and the current updates.
"USE_UPNP=-" is needed to remove UPnP support.
Merge pull request #1415 from dooglus/fix-build-unix.txt

"USE_UPNP=-" is needed to remove UPnP support.
Merge pull request #1411 from TheBlueMatt/debian

Update contrib/debian.
Merge branch 'netopt' of https://github.com/sipa/bitcoin
fix default Proxy address in Qt options (no hostname allowed currently)
fix two signed/unsigned comparison warnings in netbase.cpp
add used datadir to debug.log
Merge pull request #1422 from Diapolo/add_used_datadir_debug_log

add used datadir to debug.log
Fix DEBUG_LOCKCONTENTION
Merge pull request #1418 from Diapolo/GUI_fix_default_proxy_addr

fix default Proxy address in Qt options (no hostname allowed currently)
Merge pull request #1424 from TheBlueMatt/lockcontention

Fix DEBUG_LOCKCONTENTION