Update deb-package requirements to include libssl-dev and libffi-dev.

libssl-dev is required for compiling the scrypt python module.
libffi-dev is required for cffi, which is a requirement for bcrypt.
Pull dependencies from install_files in setup_ubuntu.sh.
Set mysql password directly. Makes it possible to run setup_ubuntu.sh multiple times.
Merge pull request #271 from ternus/ternus-setup-script

Improve setup_ubuntu.sh