Update to 1.7.99.2 (aka 1.8.0 rc1)
Changes:

• Complete refactor of the package extraction:
  • safer: ensure that only what is in the plist is actually extracted
  • ensure the package can be properly on the filesystem before actually replacing the files
  • move atomicity to the package level meaning that in case of failure only the non upgraded packages has to be proceed not the entire upgrade process
  • in case of upgrade only extract the files that are unchanged
• Now pre install script failure can properly be catched and stoping the onging process (at last!).
• New mechanism in the library events to allow frontend to know what they should run in case of interruption
• handle ^C proprely and cleanup ongoing procedure
• lots of fixes of bugs reported by coverity
• finish implementation of the 'vital' feature