Refactor the `RuntimeConfig` along with related code from libpod into
libpod/config. Note that this is a first step of consolidating code
into more coherent packages to make the code more maintainable and less
prone to regressions on the long runs.
Some libpod definitions were moved to `libpod/define` to resolve
circular dependencies.
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
