[authors] Getting Started Ch3 revised

[Jean Hollis Weber]

I have reorganised the material in Chapter 3 (File Management) of the 
Getting Started book, updated it for OOoV2.3, and added some new material. 
Because of the major reorganisation, I did not use change tracking.

I have submitted the chapter for further review.
http://oooauthors.org/en/authors/userguide2/gettingstarted/feedback/0103GS-FileManagement_JHW_18Nov2007.odt
--Jean