This commit won't build yet -- it just puts everything in a slightly
more logical place.

The reasoning here is that "src/core" will hold the stuff that every (or
nearly every) tor instance will need in order to do onion routing.
Other features (including some necessary ones) will live in
"src/feature".  The "src/app" directory will hold the stuff needed
to have Tor be an application you can actually run.

This commit DOES NOT refactor the former contents of src/or into a
logical set of acyclic libraries, or change any code at all.  That
will have to come in the future.

We will continue to move things around and split them in the future,
but I hope this lays a reasonable groundwork for doing so.

or.h should really include only the minimum of stuff from or/*,
common/*, and lib/*.

This is done as follows:
  * Only one function (find_dl_schedule()) actually returned a
    smartlist. Now it returns an int.

  * The CSV_INTERVAL type has been altered to ignore everything
    after the first comma, and to store the value before the first
    comma in an int.

This covers addressmap.h (no change needed) through confparse.h

New approach, suggested by Taylor: During testing builds, we
initialize a union member of an appropriate pointer type with the
address of the member field we're trying to test, so we can make
sure that the compiler doesn't warn.

My earlier approach invoked undefined behavior.

config_get_lines is now split into two functions:
 - config_get_lines which is the same as before we had %include
 - config_get_lines_include which actually processes %include

I'm doing this to storagedir to used config_line_t.

Also, collapse all the config_assign*() options into a flags
argument, since having two boolean arguments was already confusing.

Because in 95 years, we or our successors will surely care about
enforcing the BSD license terms on this code.  Right?

These were previously allowed only in the initial position:
  --help, -h , --version, --digests, --list-torrc-options

I added this so I could write a unit test for ServerTransportOptions,
but it incidentally exercises the succeed-on-defaults case of
options_validate too.

Also lower maximum interval without directory requests, and raise
maximum download tries.

Implements #6752.

Fix for #6113.

Note that the RFC1123 times we generate still all say 'GMT'.  I'm
going to suggest this is not worth changing.

This helps us split up one of our larger files, and sets the stage
for refactoring the configuration backend a little