Move drbuild into bin folder

This is meant to make the scrip more consistent with it's intended
location after installation. It will also be used for the future install
script in the works
Move drbuild-completion into .bash_completion.d folder

For consistency. This file should reside in ~/.bash_completion.d after
installation, so it will be in the folder of the same name here.
Add a simple installer script
Update README for new installation process