package description fields

[Ross Paterson]

Is there any difference between Homepage and Package-Url?  Can one of
them be removed?

How about moving Build-Depends to the package level (and maybe calling
it Depends)?

Is it sufficient to put License: BSD3 in the package description?
Or should License-File be mandatory, and License just an optional hint?
(Some people seem to think they should put a copy of the entire licence
in each source file. :-)

It doesn't seem to be very useful to have both a library and executables
that use it in the same package (at least with the meaning implemented
for GHC).  One has to list all the library modules again under each
executable.