allow to list and import steps independently from recipes

[npf]

Use case: I want to create a grid'5000 environment using the virtualbox/debian7-amd64 recipe. Thus, I'd like to import the export_tgz step.

[SalemHarrache]

With the current version of kameleon, the best way to do this is to list the steps used by a recipe and then do a manual copy.

$ kameleon template info default/grid5000/debian7 
Description:
 -> Debian 7 (Wheezy) image built with Grid5000 platform.
Path:
 -> /root/.kameleon.d/repos/default/grid5000/debian7.yaml
Parent recipes:
 -> /root/.kameleon.d/repos/default/base/debian.yaml
Steps:
 -> /root/.kameleon.d/repos/default/steps/aliases/defaults.yaml
 -> /root/.kameleon.d/repos/default/steps/bootstrap/g5k_reserv.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/configure_apt.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/upgrade_system.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/install_software.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/configure_kernel.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/install_bootloader.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/configure_system.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/configure_keyboard.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/debian/configure_network.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/create_group.yaml
 -> /root/.kameleon.d/repos/default/steps/setup/create_user.yaml
 -> /root/.kameleon.d/repos/default/steps/export/save_appliance_from_g5k.yaml
Variables:
 -> kameleon_recipe_name: debian7
 -> kameleon_recipe_dir: /root/.kameleon.d/repos/default/grid5000
 -> kameleon_cwd: /kameleon/build/debian7

...