Add completion for zypper pkg manager (openSUSE)

Implemented subcommand completion, global arguments completion
Not implemented yet subcommand arguments completion
Implement subcommand arguments completion for zypper package manager
FAQ: add questions from beta site
FAQ: address local variable/env usage
Squashed commit of the following:

commit bb27562af5333f84b9995b50b59c767eaae12f7c
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 04:18:09 2013 +0200

    Enhance completions for git rebase

commit e9f69ea4f9deb7a7c9284148591ff2075748ab8c
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 03:56:51 2013 +0200

    Enhance completions for git merge

commit 75974f9c2468b381069f11f8e1a03e86af1e47d7
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 03:40:27 2013 +0200

    Enhance completions for git add

commit ec6aeab105f351a6d2184078d84d32bb12df3204
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 03:16:48 2013 +0200

    Enhance completions for git tag

commit c3a1c17c436a670588a692240a562e2436538498
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 03:09:13 2013 +0200

    Add git completions for stash

commit 40baae8c75151be753da9efc309287662818d93d
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 02:54:19 2013 +0200

    Enhance completions for git push

commit 6d9023bb744f80e33481f765d542a17ecf6ccf19
Author: Terje Larsen <terlar@gmail.com>
Date:   Mon May 20 02:32:27 2013 +0200

    Enhance completions for git pull
Added darwin uname completions, fixes #778