Add an "export general AI file" button to the empire setup form

**What do you want to see?**
A button on the empire setup form that exports an SE4-style AI_General file.

**How would it help players?**
For players who still want to play SE4 instead of FrEee, they can use this tool to generate custom AI files.

**Alternatives**
Adapt the existing [AI general creator tool](http://spaceempires.net/downloads-details-466-General_AI_File_Creator.html#dldetails) for all mods. Look at that HTML... *shudders*

**Screenshots and mockups**
N/A

**Things to consider**
N/A