Several updates and fixes in Handbook's 'geom' chapter:

• Add missing messages in an example
• Avoid use of /mnt as a permanent mount point in an example
• Convert a vi editing session to a <note>
• Clearly explain how to create all types of labels (permanent, temporary, file system specific, non-file system specific)
• Add a complete example: Labeling partitions on a boot disk
• Last sector of a journaled volume stores metadata and not the log itself
• Mention loading geom_journal at startup or building it into custom kernel
• Add a reference to gjournal-desktop article
• Few other minor fixes, mostly to avoid repeating information and enhance consistency

Reviewed by: trhodes, keramida, gabor, pgj, hrs, rene, remko