Spiritus Astrum [P0-B11]: p1507: Towards Early Access

I have added several more mission objectives and events for the third campaign.

I have also written over 8 thousand words of dialog and mission briefings for the campaign, and this is just a first draft.

I am now working on integrating this dialog into the code.

I have added a menu to display the mission briefings, and I have made improvements to the dialog system to display dialog more easily during the missions.

There is still quite a bit of work to do here, but I am making good progress.

The main goals left are the artwork, and lots of testing.