Last bits

[JedMeister]

• packaging:
  • move pool to package depends - fab explicitly uses pool
  • update to modern debian compat version declaration
  • bump python version dependency
  • add additional control file fields
  • update Standards-Version
  • bump copyright year
  • rename debian/install => debian/fab.install
• imports: fix an incorrect one and remove an unused one
• wrap a long line
• cleanup some docstrings
• some extra debugging
• remove redundant use of os.path prefix (specific sub module already imported)
• product.mk:
  • introduce some indents for readability
  • bugfix bootstrap check (misplaced quotes)
  • ensure nothing is mounted in deck when "undecking"
  • check for '/' on overlayfs and give helpful error message (default behavior is not very helpful...)

hopefully we're getting close now...