[lmi] Configurable group roster showing input and values

[Greg Chicares]

I'll try to elaborate on this:
  https://savannah.nongnu.org/support/?105595
without presuming intimate knowledge of the problem domain. Let's
assume only that an insurance policy has a scalar premium that must
be paid on the day the policy is delivered, and that it covers a
person who has a name and an age; and that a number of such policies
are combined in a "group" (entered as a '.cns' file).

What our end users want is a '.pdf' report like this:

  premium  age  name
  6543.21   64  Henry Thomas
   123.45   21  Floyd Jones
   987.65   32  Bukka White

for which they can choose columns from a drop-down list. (For example,
they might want to include the person's gender, too.) I think we'd use
an interface akin to the present "File | Preferences" for column
selection: it can be a global property embodied in the
'configurable_settings.xml' file.

Every person in the '.cns' file would be represented in one row. This
'.pdf' file is separate from all others. Its name could be taken from
the name of the '.cns' file, e.g.
  'xyz.cns' --> 'xyz.roster.pdf'

That sounds pretty trivial; the complication is that the data come
from different places.

 - "name" is literally copied from class Input.

 - "age" is deduced from the birthdate in class Input.

 - "premium" comes from class Ledger.

Here's how these data come into being:
 - a '.cns' file is read into a vector of class Input; then
 - from that vector, class run_census produces a vector of class Ledger.

Class illustrator is the practical interface to class run_census; in
the GUI, it's called by CensusView::DoAllCells().

I used to think
  https://savannah.nongnu.org/support/?104490#comment1
that opening a '.cns' file and doing "File | Print preview" should
produce an html version of this report, but now I don't think so.
Reason: CensusView::DoAllCells() can take many minutes for a large
'.cns' file, and for "File | Print preview" to take that long would
be extraordinary.

Instead, I now think that requesting a group roster might work like
this:
  https://savannah.nongnu.org/support/?105907
Probably it should be produced in that case, and also by some new
menuitem that doesn't involve printing tons of individual '.pdf' files.

[An aside to problem-domain experts--it's tempting to think that we
could cover "most" of the output-column requirements without doing the
full calculations for every cell, but we do need full calculations to
print any solved-for quantity, which is a crucial case. It would be a
grave mistake to fulfill only an unacceptably-restricted subset of
users' wishes: then they'd demand whatever we omitted, and they'd
insist that it'd be "easy" because, after all, we do know how to
perform solves. Solves aren't the only reason for full calculations;
IRRs are another example.]