Introduce a new parameter for the temperature

[lpiwowar]

We're using two temperature values now:

• one value is used for situation when we do not have any hit in the vector database

• second value is used for situation when we have a hit in the vector database

We should expose both to the user. Via the API and the UI.

That's why I wanted both temperature parameters in the UI.

Originally posted by @jpodivin in #142 (comment)

[rabi]

As I mentioned in the PR I'm not sure if it's a good idea to expose too many parameters which would confuse both api and chat users.