Revent files are automatically placed in the sub folder `revent_files` in the
workload directory when recording, therefore when trying to retrieve recordings
the getter now looks inside of the sub directory.
Previously trying to use the `__base_filepath` import from inside the `Package`
class, resulted in the error "`_Package__base_filepath` is not defined."
- get_by_extension was comparing the expected extension to the entire
tuple returned by os.path.splitext(), rather than just the extension
part.
- UserDirectory getter was looking in the root dependencies directory,
rather than the subdirectory for the owner.
- Filer getter was not handling non-existing paths properly.
