Base Handbook 5.0 status report

Over the holidays I finished a quick pass edit of the updated Base Handbook
for LO 5.0. It still needs work, but I put it on the wiki as a draft, so
people could use the info in it (and report any factual errors or other
problems). Experience suggests that waiting until all the work of reviewing
etc has been done means it wouldn't get published at all.

Here is what I know still needs to be done:
- Fix the many inconsistencies and misuses of paragraph and character
styles.
- Replace some low-quality figures.
- Consider whether to put it into the v5 template. Dan Lewis did that for
Chapter 1, but the other chapters are in the old template.
- Cross check the list of sample databases given in the Preface (previously
in Ch1) with those mentioned in other chapters, and make sure the databases
themselves are included in the zip file on the wiki. At present, the list
includes several files that are not in the zip.

--Jean