Improve FIPS-Error-Messages

The File Import Service is a very powerful tool for bulk-document-imports.

Unfortunately error-messages are often unclear and/or misleading.

Examples:

• Typo in observed directory path leeds to "file <somefile_included_in_importjob> could not me moved to <destinationpath>

• missing field in key-file (8 required, 7 contained in file) leeds to misleeding message concerning some missing file, which is NOT contained in the relevant job

We would recommend a two phase error-handling:

1st step:

• Is the observed directory existing and read-and-writable?

• Does the job contain everything needed for processing?
  i.e.
  - Does the key-file fulfill the requirements of the job-setup?
  - Are all of the files to be archived available?

2nd step:

• processing of the job

• all files successfully processed and imported?