Sections: Propagate exception if obtaining key details failed

This should make it a bit easier to spot errors.
We cannot continue there if getting the key fails.
For now, we should try to support every key.
If this raises too often, we might somehow mitigate.
SignPages: Remove the scrolled window container for the QR Code

I don't know why we would want to scoll anyway. We try to display the QR
Code as large as possible.
Using the custom logic of QRCode
SignPages: Removed duplicated qr code logic

We now find all of that in the qrcode module
QRCode: Remove the data argument from the draw call
QRCode: Introduced logging
QRCode: Setting a window size in main()
QRCode: Made image_to_pixbuf a staticmethod
QRCode: Made the create_qrcode a staticmethod
QRCode: Added some documentation
QRCode: We do not need to manually call draw_qrcode

I guess because we will have at least one size request which in turns
draws the code.
Initial version of GPGQRCode, a PGP Key Barcode generator
Keyserver: Made it bind to IPv4 *and* IPv6 socket

The ThreadedKeyserver inherits from BaseHTTPServer which itself is a
TCPServer.  It uses a bind_server method to allocate the socket.
Apparently there is a IPV6_V6ONLY option which determines whether
a IPv4 socket should also be bound.

According to very simple testing, it does indeed bind to both,
IPv6 and IPv4 addresses.
Merge branch 'ipv6' into keyserver

We want it listen on both, IPv4 and IPv6 sockets.
QRCode: Made the widget a DrawingArea for proper resizing

There was a problem when maximising the application and then resizing it
back to its original size, i.e. Super+Up and then Super+Down.
The window would not go back to its size, but rather stay larger.
With this change, it works much better. Thanks benzo.
SignPages: Removed duplicate QR Code drawing logic
QRCode: Made it open a fullscreen window on click
QRCode: Closed the window on keypress

So far, it is Escape, F, or Q.  But that's a bit arbitrary and can
be amended.  In fact, any key might be an idea.
Merge commit 'faf5a071ad439ce5c16103f8d845f8d0c28cb59e' into master_qrcode

for preparation of merging into the master branch

Conflicts:
	SignPages.py
	    Basically only imports at the top.  For some reason, it thought
	    the qrcodeLabel had changed.
Merge branch 'master' into master_qrcode

Updating the new qrcode code for use in the master branch.