adding privacy and comments to Notes

This issue is based on the blog post here (http://blog.civicrm.org/blogs/allenshaw/adding-privacy-and-comments-civicrm-notes) and the forum issue here(http://forum.civicrm.org/index.php/topic,15229.msg65163.html#msg65163).

These points may be worth mentioning:
1. Table sorting with comments requires jQuery DataTables 1.7.0 or higher, but this patch does not include that upgrade.
2. Note privacy options are option-value pairs in the option_group 'note_privacy', but no UI is provided to edit them. Out of the box, two privacy levels are provided: "None" (0), and "Author Only" (1)
3. New permission "view all notes" bypasses any privacy limitations, and bypases hook_civicrm_notePrivacy()