documenting gncVendor (freshman effort)

[Rich Johnson]

OK.  So far I've retrieved HEAD and sorted out build dependencies 
(thank you debian).
I've also installed doxygen (what a pig...I had to enable swapping; but 
it works) to populate src/doc/html--a live public link to this 
work-in-progress is http://workshop.dogstar-interactive.com/gnucash/   
(Note:  the contents will be occasionally unavailable during 
regeneration.)

My first round is an attempt at documenting gncVendor's accessors at 
http://workshop.dogstar-interactive.com/gnucash/group__Vendor.html

I'm still bootstrapping so I'd appreciate comments on style and content 
before I generate and post the diffs.

Now for the meat:
  - What are the semantics of TaxIncluded/TaxTable/TaxTableOverride.  
What is the tax table overridden with?  Or does this flag mean that the 
tax tables are to be ignored.?
  - What are the semantics of Active?
  - What _exactly_ is an owner, and how should it be used?  It seems to 
be a weak reference (or proxy) for a vendor/customer/Employee/etc.

all for now...
--rich