add clarifying game create / start message

#### What's this PR do?
Adds a new opt in path for a potentially confusing situation: the user when creating a game, is prompted to add beta players. When the user adds a beta, the alpha is then asked if she wants to create the game witout adding more betas. 

This is confusing, because the user may think that answering 'Y' to this query is in fact **starting** the game, when in fact she's only **creating it** and more users need to join. 

This is simply adding a new opt in path which clarifies the situation to the user. The user is opted into this path after they answer 'Y' to the message asking if they want to create the game now. 

#### How should this be manually tested?
Via mobile phone.