Trying to address what these configuration files really do.
This change allows to see the short description that mention
the purpose of the content in the config file and obtain
them through API.

This change also encourage one who want to make some UI for
the user-specific configuration management. it is the main
purpose of this change for me though.

Aside from that, I've also made programs translatable. so
we see more dependencies on the build time for gettext,
and itstool to generate PO from xml.

Move the target of recipes to the "pattern" from the "font".
This is to ensure the targeted objects is updated by them
prior to FcDefaultSubstitute() so that it can adds the default
values properly.

Use "append" to avoid overwriting the user configuration.
This presumes most clients may takes care of the first value only.

Conf files had an initial comment mentioning the files' name.
This was outdated and wrong in most cases.  There's no real use in that.

Most of the remaining elements in fonts.conf have been moved to separate
files. The numbering scheme for conf.d files has been documented in the
README and the files have been renumbered. Config files have been
validated against the DTD and a few minor errors fixed.

Make sure they continue to load after ~/.fonts.conf and local.conf

Make sub-pixel.conf be sub-pixel-rgb.conf and add the
three other possibilites: bgr, vrgb and vbgr.

All of the files in conf.d are now in conf.avail
Makefile.am is updated to reflect the change

Sub-pixel configuration examples must smash subpixel value as Xft always
    sets it from X.
Change sub-pixel rendering debconf descriptions from Enable/Disable to
    Always/Never.

    configuration files. Deprecate use of local.conf for local
    customizations in favor of this directory based scheme which is more
    easily integrated into installation systems.
Tag FC_EMBOLDEN as a boolean variable