* [WIP] Unpack local docker images
* unpack local image
* PR feedback + missing new function call
Co-authored-by: Ettore Di Giacinto <mudler@users.noreply.github.com>
This commit is multi-fold as it also refactors internally context and logger
as interfaces so it is easier to plug luet as a library externally.
Introduces a garbage collector (related to #227) but doesn't handle yet
parallelism.
Closes#265
tarball.LayerFromReader slurps the whole src in memory. The payoff is
that we might read the file multiple time as internally it's called
multiple times.
It holds necessary state plus additional information relative to the
context which we are being run to (e.g. if we are in a terminal or not).
Besides in the future we can use it also as a contextual logger to
provide more smart logging capabilities.
This also replace the general global configuration instance that
previously was share between the core components.
