FTN nodelist browser

Replaces 'ftnnv' thing that's been floating around.
Loads any nodelists you've configured in echocfg/sbbsecho.ini.
Has a search feature, let's you send netmail.

You can optionally add this section and any keys to modopts.ini:

[fido_nodelist_browser]
auto_close_domain = true
auto_close_zone = true
auto_close_net = true
nodelist_a = /path/to/some/nodelist
nodelist_b = /path/to/some/other/nodelist

The auto_close settings control whether branches in the lightbar tree are
closed when you open another at the same level.  The defaults are more
memory friendly.

If you have nodelists not known to sbbsecho (or aren't using sbbsecho 3)
you can add them here; the key must begin with 'nodelist_'.  Wildcards
are not supported; you should have some external mechanism copying the
current nodelist to a fixed path & filename.