use existing method to change event background
small speedup by removing double layout of times column

The times column is laid out in onResume() anyway to update the current
time.
skip action on chooseDay() if the current day stays the same
Don't replace fragment if it already exists (on orientation change)
reduce number of views displayed by usings margins instead
remove unnecessary linear layout from time column elements
fix background colors, room header actually had none
display if an event has opted out from being recorded