Allow control characters in JSON string literals

This is to allow multi-line base64 encoded data in the "contents"
attribute of img_personality.

Fixes #51
Add Brian Candler to the authors list
docs: Fix a minor typo in the Interface section
pithcat: Add support for Archipelago images

Synnefo version 0.16.0 completely removes the selectable storage backend
for Pithos, and introduces an integration with Archipelago, resulting in
necessary changes to the ModularBackend class.
In order to keep backward compatibility with older Synnefo versions, we
check the Pithos backend version and instantiate the ModularBackend
class appropriately.
pithcat: Fix a bug when using Synnefo version 0.16

PITHOS_INPUT_DATA env variable and '--data' option are not used
in Synnefo version 0.16.
Update some links to use https in favor of http

Update all apt.dev.grnet.gr and cdn.synnefo.org links to use https