Revert to using in memory database for development.

Negates 0be70ae.
Add method for retrieving users by id.
Add method for removing players.
Move player creation to the player view.

Also switch to using select boxes for the player names when adding new games.
Make it possible to delete existing players.
Restyle the players view and add a new player form to it.
Remove non functioning placeholders on selects and add options instead.
Adapt columns to not stack until using small devices.

i.e. use the col-md class instead of the col-lg class to still use columns on medium screens.