Initial commit of bash-completion 2.1

This is an initial addition of the bash-completion macros maintained by Debian as I need this to handle the environment-modules in a clean way.

- Some macros are not useful on OpenIndiana and other might need modifications but at least this commit would give the possibility for people to get started with.
- A variable BASH_COMPLETIONS_PATH has been added to shared-macros.mk to allow installation of macros by other packages in the same directory.

As it is my first addition to oi-userland I would appreciate your comments and advice on the best practices.
Best regards,

Aurelien