Moves the config file to a config submodule.  This allows us to easily
separate out the configs for each environment, as well as the config
vars that are shared.  This is also structured to retain the ease by
which setup_ubuntu.sh replaces vars using sed, by having different
environment configs being separated into different files.
Modifying setup_ubuntu.sh to modify config files in new location
MySQL credentials should be replaced with the actual created user in
the setup_ubuntu.sh script for the development environment, not the
test environment.
Update HACKING.md to reflect new config file locations
abspath should refer to securedrop/securedrop path
Removing line changing SECUREDROP_ROOT dir for test.py.example in setup_ubuntu.sh
Fixed unneeded create database for test in setup_ubuntu.sh
Merge pull request #219 from Hainish/issue211

Makes config a module, with different files for development / production / test