Attempt to fix v1.2.0 crash

v1.2.0 was rebuilt on macOS Big Sur -> v1.2.1. Hopefully, this fixes the crash reported in issue #2.

Better handling of daylight savings time (DST)

• Removed redundant (separate) time zones with DST offsets from the list of all zones. Zones that use DST will now only show up once in the list of time zones.
• New column added to clocks table to display when the next DST transition will occur.
• New option to indicate DST (when active) in the menu bar clock display.
• Minor UI usability improvements - better captions, new menu icons, etc.

NOTE - With this release, your previously added clocks will be lost, and you will need to add them in again.

Ability to edit clocks

• Added the ability to edit clocks
• Persist settings on every update
• Added tool tip to menu bar button
• Better source code structure within project

First release

First release of World Clock.