Frontend improvements

[mwien]

• After switch to guessing phase the bottom of the main box moves up a few cm
• Make width of game input (clues/name) adjustable and different for these two cases
• fixed width for name in player components
• add settings and help icon in header
• Polish player_component.ex
• min height of text placeholder for empty strings (should be 7.5)
• Look at fonts -> maybe style heading with shadows
• Add IDs for rounds and make form elements unique over rounds (for browser autocomplete)

A larger UI rewrite might not be such a horrible idea...