Remove use of IncidentSvc in DataSvcFileEntriesTool

Closes #102. Not marked WIP because it's done as far as I'm concerned, but I'm fairly sure this won't be an acceptable solution for every. Am opening the MR to generate some discussion and hopefully move towards a consensus on how to address #102.

The changes here represent a third option not listed in #102, which is to just removing the IncidentSvc-based caching in the tool directly (so, most similar to option 1). Note that, as stated in the issue, this solution:

…suffer[s] from the problem of not being able to robustly check if an OutputStream instance has been run before an InputCopyStream instance (which can cause problems, was tracked by Savannah ID 76642).