Added a popup to both start and end times with Phrequent allowing the user to edit their start/end times. Also added a field for notes on the stop time

Summary:
I have added a dialog box which pops up when a user starts or stops tracking time on an issue with Phrequent. These dialogs allow the user to modify the time if it so happens that they forgot to either clock in or out.
I have also added a Note field in the dialog when a user stops tracking time. This allows them to enter a note about the time, and is entered into the database, but is currently (as far as I know) not visible anywhere in Phabricator.
I have made these changes according to the suggestions found in T3568

Also, upon clocking in or out, if the time entered is a future time, an error is returned and the user is asked to enter a valid time.

Test Plan:
Start tracking time and edit the start date/time, then end the time and edit that timestamp as well.
Also, try entering future dates/times and ensure that the dialog reports an error and asks for the time again.
Ensure that these edited times are recorded properly.

Reviewers: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T3568

Differential Revision: https://secure.phabricator.com/D9147