Add support for campaign status

[kubaau]

Adds support for Roman-style (video) campaigns and the world campaign (video).

Fixed world campaign scripts to unlock the same continents as it was in S2.

Related to issues #1639 and #1177

[Spikeone]

Either I'm blind or the implementation is somewhere else? What is rttr:SetCampaignChapterCompleted good for?

[kubaau]

Either I'm blind or the implementation is somewhere else? What is rttr:SetCampaignChapterCompleted good for?

~~It doesn't make a difference in Roman-style campaigns, but~~ it marks a continent as conquered in the world campaign. It could also be used for other campaign types as well if we wanted to show what was completed, especially if someone designs a campaign whose progression is not linear.

Edit: For roman-style campaigns it shows the "You have successfully completed chapter X." screen after ending the game.

[kubaau]

Rework in progress - converting to draft, will notify when ready for review. Resolving some conversations since they will not be relevant.