Enhancements to SimpleFileExtractor

[prioux]

As mentioned in PR #1131

Possible enhancements:

1. allow the admin to extract files that are not local
2. allow a normal user to extract files that are not local if the total size is < some threshold?
3. add flags that tell the task to fail immediately if any subset of the warning conditions happen (e.g. stop if there is a collision, or stop if a pattern doesn't match anything
4. create non-flat outputs, where when a file is extracted, a subdirectory creation pattern can be provided for it
5. extract subfolders (see Extract folder from file collection #1076)
6. support for CbrainFileLists in input
7. check for input file collections to make sure they are not archived
8. allow the program to clear the caches after files are extracted, or even during extraction
9. provide extraction statistics

See also #229