Merged from trunk 8251:8259

   Merged from trunk 8251:8259

   | 8252    | protect variables specified in PROFILE_ONLY_VARIABLES from   |
   | genone  | being set by the user                                        |

   | 8253    | make PROFILE_ONLY_VARIABLES incremental                      |
   | genone  |                                                              |

   | 8254    | make 'world' and 'system' behave like their sets/            |
   | genone  | counterparts                                                 |

   | 8255    | Optimize PROFILE_ONLY_VARIABLES handling.                    |
   | zmedico |                                                              |

   | 8256    | just pass the SetConfig instance instead of only the         |
   | genone  | settings and trees attributes                                |

   | 8257    | move base classes for package sets into a separate module    |
   | genone  |                                                              |

   | 8258    | revert r8256 (plans changed)                                 |
   | genone  |                                                              |

   | 8259    | document PROFILE_ONLY_VARIABLES                              |
   | genone  |                                                              |

svn path=/main/branches/prefix/; revision=8273