Fix time centering in overlay

[TristanDebrunner]

Currently, when a time is displayed, the entire time string (ie "12:34") is centered in the spot we want it. Because we are not using a monospaced font, as the time counts down the colon shifts left and right as the digits change widths.

Proposed Solution:
Split all time displays into three parts: the minutes, the colon, and the seconds. Then, draw them all separately:

• Minutes justified right
• Colon justified center
• Seconds justified left

This will lock the colon into the correct center spot, and the digits will be displayed correctly relative to the colon