Squashed commit of the following:

commit 8b84a4137b80f59867856eceb1a2603fb9e87650
Merge: d213bfd a42fa0e
Author: George Cox <gjvc+git@gjvc.com>
Date:   Fri Apr 4 03:22:37 2014 +0100

    Merge branch 'wip' of github.com:gjvc/commander into wip

commit d213bfd4010d89f03888a0835d7f4d2f42a2fd4b
Author: George Cox <gjvc+git@gjvc.com>
Date:   Fri Apr 4 03:13:12 2014 +0100

    hierarchical navigation of configuration namespace

    get a basic tree-structured command-line shell working, via ls and cd
    commands, which are the moral equivalent of their UNIX namesakes.

    this actually could enable one access to the equivalent of the control
    and data planes, in time...

commit a42fa0e54a98376fa59a93b6f3440fa506ef037e
Author: George Cox <gjvc+git@gjvc.com>
Date:   Fri Apr 4 03:13:12 2014 +0100

    hierarchical navigation of configuration namespace

    get a basic tree-structured command-line shell working, via ls and cd
    commands, which are the moral equivalent of their UNIX namesakes.

    this actually could enable one access to the equivalent of the control
    and data planes, in time...

commit c0cefbf547880d0d999d499cbe4c9d670c8ed0e0
Author: George Cox <gjvc+git@gjvc.com>
Date:   Thu Apr 3 23:57:32 2014 +0100

    cleanup imports

commit 487f599d5d4488bdc2a29b7acfa9731e6daf4f96
Author: George Cox <gjvc+git@gjvc.com>
Date:   Thu Apr 3 17:43:50 2014 +0100

    use TypeError

    Use TypeError, not an application-level exception such as
    InvalidPrototypeException based on CommanderException

commit d6eb5dee785fc364827513a7df024ed33b43df07
Author: George Cox <gjvc+git@gjvc.com>
Date:   Thu Apr 3 02:09:06 2014 +0100

    lexers

commit 2d061236402038700cfaf9c45a875d66f389351f
Author: George Cox <gjvc+git@gjvc.com>
Date:   Thu Apr 3 02:08:44 2014 +0100

    latest

commit eb1a0b14290977c93a21c13f9590d2974d50a434
Author: George Cox <gjvc+git@gjvc.com>
Date:   Wed Apr 2 22:15:38 2014 +0100

    enable hashing of properties

commit c6e9d0354a6b78278890afa0f8f9321c60193e86
Author: George Cox <gjvc+git@gjvc.com>
Date:   Wed Apr 2 19:07:59 2014 +0100

    refactor Message