Support these new cards in slots 3, 4 or 5; based on code from Lukazi.
- extend Configuration's Input prop sheet page.
- add save/load snapshot for both cards.
- add command line switch for alt controller type (for SNES MAX card).
Change to using Registry's 'Configuration\Slot 3' for slot 3 cards (Uthernet, 4Play & SNES MAX).
Update help doc.
Change to using Registry's 'Configuration\Slot n' for disk ii image pathnames (was 'Preferences').
Delete Registry's 'Configuration\Slot n' section each time there's a change of card.
Add same functionality to conf.ini.
LoadConfiguration(): load from the new Slot-n section (or otherwise the old legacy key).
Only update Registry's 'Starting Directory' for s6,d1.
Update help doc.
. added documentation for right mouse context menu (eg. for Eject, Send to CiderPress). Fixes#258.
. added documentation for using Open-Apple key to boot from floppy instead of hard disk.
. renamed harddisk to hard disk
