D-Day Decisions prioritized to top of intrigue menu

I also had to disable [almost] all realm_decisions until the first day
passes in order to prevent, e.g., an un-executable "Hold a Grand
Tournament" from displaying over the D-Day Decisions
(00_PB_customization.txt), as all but two of them (which are not
delayed accordingly) cannot be executed on day 0 (without cheating, at
least, and in cases where that might still make sense, they are
extremely low-priority for a day 0 execution) and are often
is_high_prio=yes.
NAE: Bulgarian Empire properly removed in 867
Merge pull request #92 from zijistark/dev

Queuing some fixes.