Fixes how current task end time is updated

Refactors the name of the task list variable. Length of list is checked
each time a new task is started. If the list is not empty, the last task
on the list is given the current time as its end time. That task does
not need to be added to the list again.
Adds time information to displayed task list

If the task is ongoing, the start time is appended to the end of the
task name. If the task has already ended, the task duration is appended
to the end of the task name.
Gradle updated

Updated file permissons on gradlew so `./gradlew clean` can be run.
Other misc updates that Android Studio applied automatically after the
clean I performed in order to get the app to run with the new
dependency.