[Qt] let OptionsModel::getProxySettings() directly query proxy

- as a proxy set via GUI can be overridden via -proxy, directly query the
  core to get active proxy
- give a warning, if active proxy is not SOCKS5 (needs to be SOCKS5 for
  the Qt networking code to work)
- also remove an obsolete connect() call from optionsdialog.cpp and a
  reference to Bitcoin-Qt (now just GUI)
qt: allow `walletpassphrase` in debug console without -server

Currently it is only possible to use `walletpassphrase` to unlock the
wallet when bitcoin is started in server mode.

Almost everything that manipulates the wallet in the RPC console
needs the wallet to be unlocked and is thus unusable without -server.

This is pretty unintuitive to me, and I'm sure it's even more confusing
to users.

Solve this with a very minimal change: by making the GUI start a
dummy RPC thread just to handle timeouts.
Fix importprivkey / rescan
wallet: add interface for storing generic data on destinations
[Qt] Permanently store requested payments in wallet
[Qt] Add sorting feature to the requested payments table
gitian: Windows 64 bit support

- Build a 64 bit version of all dependencies
- Show 32/64 bit version in "About..." for x86
- Export 64-bit .exes and installer from gitian build
Adapt Windows installer for 64 bit
build: Add bitcoin-cli.exe to installer
build: Package docs/ and don't package source.

No-one uses the installer then builds from source.
Closes #2819.
build: Change package name to Bitcoin Core

Affects the name of the package as shown in installers
and such.

Also rebrand the windows installer.
Merge pull request #3502

1f12844 Fix importprivkey / rescan (Cozz Lovan)
Merge pull request #3521

4d90102 [Qt] Add sorting feature to the requested payments table (Cozz Lovan)
8476d5d [Qt] Permanently store requested payments in wallet (Cozz Lovan)
b10e147 wallet: add interface for storing generic data on destinations (Wladimir J. van der Laan)
Merge pull request #3452

1ba3560 [Qt] let OptionsModel::getProxySettings() directly query proxy (Philip Kaufmann)
enable full GCC Stack-smashing protection for all OSes

- change our hardening options to use -fstack-protector-all even for
  Windows builds, as we recently switched to a newer compiler suite
- also removes an obsolete workaround for GCC 4.5
  (https://bugs.launchpad.net/ubuntu/+source/gcc-4.5/+bug/691722), which
  required to first set -fno-stack-protector, before -fstack-protector-all
[Qt] very minor style cleanups

- rebuilt some ui file layout to remove unreal values from the files
- remove an unneeded attribute from an ui file
- add / remove some spaces in files
build: Add -static for mingw builds

This avoids a dependency on libssp-0.dll when built with
-fstack-protector-all.
Merge pull request #1674

6ac0b3b build: Add -static for mingw builds (Wladimir J. van der Laan)
4e57e23 enable full GCC Stack-smashing protection for all OSes (Philip Kaufmann)
Merge pull request #3567

22a5120 [Qt] Show and store message of normal bitcoin:URI (Cozz Lovan)
Merge pull request #3568

4bee715 [Qt] very minor style cleanups (Philip Kaufmann)