[QT] Don't ask for a passphrase to getnewaddress.

With an encrypted wallet the GUI was prompting for a passphrase every time
 the user requested a new address.  This is unnecessary, increases the
 exposure to keyboard sniffers, and discourages using fresh addresses for
 every transaction.

Instead only prompt for a passphrase when the keypool runs out, also call
 the new address function with the flag that prevents reuse.

Thanks to AlexNagy on IRC for pointing this out and who wouldn't take any
 lip from a curmudgeonly developer and insisted on what he knew to be true.
Remove fAllowReuse from GetKeyFromPool.

With the GUI password fix this was always false.
Bitcoin-Qt: add testnet check and icon to intro dialog
move Checkpoints:fEnabled from step 2 to step 3 in init

- it belongs to parameter-to-internal flags step, not parameter
  interactions phase
Set Accept: application/bitcoin-paymentrequest header

Suggestion from BitPay: set an Accept: HTTP header when
fetching payment requests / payment ACKs.
Merge pull request #2904 from gmaxwell/newaddr-no-passphrase

[QT] Don't ask for a passphrase to getnewaddress.
Merge pull request #2931 from Diapolo/intro

Bitcoin-Qt: add testnet check and icon to intro dialog
RPC: add getrawchangeaddress, for raw transaction change destinations
Bitcoin-Qt: fixes for using display unit from options

- extend PaymentServer with setOptionsModel() and rework initNetManager()
  to make use of that
- fix all other places in the code to use display unit from options and no
  hard-coded unit
Merge pull request #2940 from Diapolo/checkpoint

move Checkpoints:fEnabled from step 2 to step 3 in init
qt: Handle address purpose in incremental updates

Correctly use the purpose of addresses that are added after the start
of the client. Addresses with purpose "refund" and "change" should not
be visible in the GUI. This is now handled correctly.
Merge pull request #2930 from Diapolo/displayUnit

Bitcoin-Qt: fixes for using display unit from options
qt: Add comment to sorting step in refreshAddressTable
Add "mkbootstrap" script to contrib, for creating bootstrap.dat.
Merge branch 'mkbootstrap'
contrib/misc/mkbootstrap: rename to linearize.py
qt: Use GUIUtil::HtmlEscape to escape HTML

This is why we created this function. Avoids some #ifdef.
Merge pull request #2955 from laanwj/2013_08_htmlescape

qt: Use GUIUtil::HtmlEscape to escape HTML
fix help prompt
Merge pull request #2957 from Rav3nPL/patch-1

fix help prompt