Leaders & Civs Rewrite

[kjniemela]

Most of the dirty work of #183 is done.

Essentially, the Leader and Civilization classes have been swapped, taking each other's roles in most cases.

Leaders:

• Own any number of Domains (which can be either Civilizations or Cities)
• Keep track of turns.

Domains (Civs and Cities):

• Control a list of units.
• Have one Leader, or null.

Civilizations:

• Have a name and a jersey color.
• Have unique starting knowledges.

The DomainID type was added, which contains information about both the type of domain as well as a numeric ID (subID) for the domain. The subID is not globally unique, it's just unique within the specific DomainType.

[kjniemela]

I'm going to merge this, but I'll add it to the task board and assign myself to it so we don't lose these comments.