elementary: embed standard config as fallback

elementary: embed standard config as fallback

Summary:
as you can see in T7620, there is quite some critics about how we are
handling configs in elm. This patch enables the compile-time standard
config to be used instead of some weak-wrong-usage hardcoded structure
defines somewhere in elm.

This means, that every update to the default theme will be also in the
next build embedded, without any config files installed at all, the
standard config for desktops will work, and a error will be printed, so
the user does have the possibility to interact with elm as he wishes,
while he sees this error.

fixes T7620

Reviewers: zmike, cedric, segfaultxavi, devilhorns

Reviewed By: zmike

Subscribers: devilhorns, #reviewers, #committers

Tags: #efl

Maniphest Tasks: T7620

Differential Revision: https://phab.enlightenment.org/D8481