Replaced "characters" with "names"

Replaced the characters section in project options with a more generic names, and adapted the instructions and prompt generation to reflect the change. Characters in older project files should be transferred to the names section automatically.

Note that the base gpt3.5-turbo models are likely to ignore the provided names completely, but the turbo-instruct models are somewhat better at recognizing when to use them, and gpt-4 will probably use them correctly and consistently.