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.
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
Add a CHub for communication from p2p/wallet to blockstore.

The goal is for p2p code/wallet to only get information/communicate
information about the blockchain through CHub, giving Bitcoin a
much more clearly-defined structure and allowing for the removal
of a ton of the current global mess.
Add a basic CHubListener that can be extended.
Add AskForBlocks/RegisterAskForBlocks functionality to CHub.

Creating a callback to request blocks from peers.
Add EmitBlock/CommitBlock functionality to CHub.

Replacing ProcessBlock with EmitBlock, and creating callbacks for
CommitBlock.
Fix typo
Add CWallet support for registering with a CHub.
Add CWallet::HandleCommitBlock and move junk from main.cpp to it.
Add HandleCommitBlock to net.cpp & move stuff from main.cpp to it
Remove uiInterface.NotifyBlocksChanged and replace with CommitBlock

Also rename NotifyBlocksChanged to NotifyNewBlock and remove from
the uiInterface signals list.

This removes some functionality, but NofiyBlocksChanged was not
used anyway, so it shouldn't matter.  That said, if it is ever
needed, it would be fairly trivial to add a new callback for it
in CBlockStore.
Add EmitAlert/CommitAlert functionality to CHub.

Replace ProcessAlert with calls to EmitAlert and create callbacks
for CommitAlert.
Use CommitAlert in qt/clientmodel.cpp
Add RegisterRemoveAlert functionality to CHub.
Replace NotifyAlertChanged with RegisterRemoveAlert.
Convert Orphan Tx storage to CTransactions from CDataStreams.

There was no reason to use CDataStream as the transaction was
already being serialized/deserialized several times, with this
change, transactions coming in over network are deserialized once
when received, and then only reserialized in the call to
RelayMessage, which will be called in a callback thread, not
blocking cs_main.