Add support for custom entry formats

[toomeyDev]

Current entry formats involve using presets (separate prompt for hrs minutes seconds each on a separate line, condensed prompt for hrs minutes seconds on one line etc) to change the user's time entry format. Allowing the user to choose any combination of times (only hours, only minutes, only seconds and hours and so on) would allow for the time clock to be more configurable and meet more use-cases overall.

Likely to require separate functionality (functions, formatting) from the currently existing entry format settings.

• Implement system for selecting custom time formats

[toomeyDev]

No longer applicable given current GUI implementation, development on this issue should be moved to https://github.com/toomeyDev/SimpleTimeClockCLI.