[Patch] Schedule-list remembers selections + small upgrades

[Dwachs]

with this patch the schedule-list-gui remembers the selected tab as well as the selected lines for each tab. This data is stored in spieler_t.

More features:
=== disables the 'new line' button if the 'all' tab is selected, no more error messages 'cannot create line for type all'
=== changed the appearance of the selected tab, since it was not easy to recognize, which tab is selected