Default countdown mode set to time of day except countdown after upgrade

[lukaslangrock]

When users upgrade to 1.3, the settings file does not include a parameter for which countdown mode to use, so the settings gets added and a new boolean initialized, meaning CountdownMode is set to false on upgraded installations, resulting in time of day being the default mode.

New users start with completely empty settings and therefore get the recommended default of ``true` for this setting.

[lukaslangrock]

I'll probably also force migrate this to true for people coming from 1.3.0. Any users who intended this to be default in their setup will probably figure this out, but the vast majority is probably confused at the new behavior and either change this manually every time or reconfigured the settings. I expect the negative impact from this bug to be lessened for most people this way.