24 Hour Time Added to Preferences and Functionality

[jackw00]

Related issue

Closes #10

Context / Background

• The purpose of this PR is to add a button on the preferences page that allows users to switch back and forth from 24 hour time mode to 12 hour AM/PM mode. When in 24 hour time mode the monthly calendar appears the same as in 12 hour time mode, except users can enter their time in 24 hour format, and don't have the option to select AM/PM.

What change is being introduced by this PR?

• Added a button on preferences HTML and js. Based on preferences, a different validate time function in time-math.js is called for 24 hour time. Based on preferences, the HTML (loaded via JavaScript) and JavaScript in base calendar and monthly calendar loads a different input box and fetches the input from these input boxes using a different label.

How will this be tested?

• Built in test cases. Added test case for changing to 24 hour time.

[tupaschoal]

Hi @jackw00, thanks for your contribution as your first PR?
Would you mind posting a short gif/video showing how the feature works now?

[araujoarthur0]

Ping @jackw00