hob: The title of the packages screen depends on the screen you arrive from

hob: The title of the packages screen depends on the screen you arrive from

- If you arrive to the packages screen from the recipes screen, the title
should say: 'Step 2 of 2: Edit packages'
- If you arrive to the packages screen from the image details screen, the
title should say: 'Edit packages'
- The title of the recipes screen should say 'Step 1 of 2: Edit recipes'

[YOCTO #2982]

Signed-off-by: Constantin Musca <constantinx.musca@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>