[authors] Changed location for User Guide 3 files

[Jean Hollis Weber]

For reasons too tedious to go into here, I had to change the location 
of the folders for User Guide 3 to:

http://oooauthors.org/en/authors/userguide3/
I recommend using a bookmark for this. Otherwise you need to click on 
the User Guide tab (under the OOoAuthors logo), which takes you to 
User Guide 2, and then scroll down a bit to get to User Guide 3.

--Jean