status: divide the code into small chunks & add an offline mode

This change divides the huge `runStatusAll()` function into small
functions with specific re-usable blocks. The new re-usability enabled
addition of an offline status mode which generates the same status only
from the manifest and lock file only, without any upstream project
knowledge. This offline status is completely compatible with the existing
`-json`, `-dot` and `-f` flags.

Author: darkowlzz