Changes to make to API when we are ready to make backward incompatible changes:

- HTMLReport has special API for more context on columns and special handling in REportGenerator. Change all reports to the new API.
- Content.getUniquePath() should not thrown TskException.  We should deal with it in the method.
- Make the list of events that Case fires off to be part of an enum to group them together (like IngestManager does).