Update appliance/README.md conforming to the new folder structure.
Rearrange all README.md scripts in appliace/ .

* Remove Docker/ directory as useless, with README not really providing any
  informations but fuffa.
* Remove Vagrant/ directory as useless, with README not really providing any
  informations but fuffa.
* Move Packer/README.md into appliance/, and merge with its readme.
Move appliance/Packer/ to appliance.

The old directory structure at this point has become meaningless. I'm moving
Packer/ to ./ .

Vagrant images are going to be generated from packer, so at most they will be in
a child directory.
Docker is not really a target currently.
Package python-pip is required to run globaleaks.

GlobaLeaks attempts to import pip to assert that all dependencies have
been installed; otherwise, it will fail.
Use "install_requires" instead of "requires" in setup.py.

install_requires is used to generate requires.txt file, later read by
dh_python2, and then guess ${Python:Depends}. No idea what that generic
"requires" is useful for.