Status indicators

Adds ability to create status indicators in the top right, currently this is only used to display **PAUSED** if the game is paused, but is flexible enough to allow the display of (almost) any message. To add additional messages, call statustext.add({priority, callback, text}). Low priorities get displayed before high priorities, callback is used to determine if the text should display (it should return either StatusText::EMIT if the text should be shown or StatusText::PASS if it should not, and either StatusText::KEEP if the callback should be kept in the queue to be evaluated later or StatusText::REMOVE if it should not. Example: return StatusText::EMIT | StatusText::KEEP;). Once EMIT is returned, it displays that text and stops processing the rest of the queue.