KNGConfigItem.__init__: explain defaults

I keep wanting to use the defaults dict here, but that
is actually not appropriate (indeed, thusfar, that dict
has no actual use -- I just suspect it will become useful
later).

Explain why only the default value provided to the constructor
is relevant here.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
kernelng/config: poorly explain format of mapping tuples
config: example: add explicit global section

Now that (most of) the infrastructure is in place to merge explicit
and implicit global sections, go ahead and add an explicit global
section to the configuration file.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
config: example: drop superfluous whitespace

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
config: KNGConfigItem: comment about 'value'

comment discussing the relative merits of creating a 'value' property

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
config: KNGConfig: fix indentation mistake

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
config.subconsts: use echov

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfigItem: better comment about value

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfigItem: add reason setter

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGExampleConfigData: better introductory text

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGExampleConfigData: nameprefix -> name_prefix, no_name_prefix

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGExampleConfigData: /dev/null -> empty with explanation

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGExampleConfigData: fix whitespace typo

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGExampleConfigData: add name_override/no_name_override example

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfig: support four-item tuple syntax

The example tuples are now in the format:

 (<key>, <value>, [<force-stored>, [<non-default>]])

support the new non-default boolean programmatically.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfigItem.__repr__ implementation

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfigItem: drop encapsulation comment

Drop the in-source comments stating that the KNGConfigItems can't know
about the section.  Although this will still be mostly so, we are going
to somewhat relax this soon with the introduction of the daddy mechanism.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
KNGConfigItem, KNGConfigItems, KNGConfig fetal/daddy support

This patch fine-tunes the semantics of containment, pseudo-dict
behaviors in KNGConfigItems, and the default/reason/value state
machine.

Well, it's frankly still a mess. But this is enough to get started.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>