[FileEncap18] Clean up uploading scheduling

- Move scheduling logic from ResearchLogger.java to
  UploaderService.java
- Switch to a one-shot timer.  Previously the uploader was scheduled
  on an inexact repeating schedule.  It's better to reschedule the
  next upload after the current one is finished to reduce the chances
  of multiple uploads happening at the same time.
- Avoid double-execution
    - Previously a scheduled upload might run right after an explicit
      one if they occured at the same time.  This change reduces the
      chances of this.
- Some method extraction and naming

Change-Id: I9efda11be77d334c7f61bd40a36d65f0421ebde4