Add the Status Command

* Add the `status` command to hkredmine, showing the user the current
  account, issue and tracked time.
* Add the getTrackedTime function to calculate how much time has been
  tracked on the current Issue.
* Add the appFileExists function to check whether a file in the User's
  app data directory exists.
Cleanup the Version Detail Display

* Modify the versionDetail function so that the versionDueDate and
  versionDescription are only shown if they are not blank.