GeezerVison

The AOD reader replaces every occurrence of the
aod-parent-base-path-replacement pattern in a parent file path, while
metadata discovery replaced only the first one, so the two could open
different files. Use the same replacement in both. An empty pattern is
now ignored, as it is in the reader.

With --aod-origin-replace and --aod-origin-level-mapping, every device
received the metadata of level 0, even when different files are read.
Each device now sees the metadata of the level its origin maps to.

- Parse and validate aod-origin-level-mapping once during discovery, into
  the aod-origin-level-map LabeledArray which the AOD reader now consumes.
- Read each mapped level through AODInputFile, opening every file in the
  chain of parents only once, and forward the result as the
  aod-metadata-origins LabeledArray and aod-metadata-origin-<O>-tables.
- Overlay the row of the origin of the process on the plain
  aod-metadata-* options at the end of discovery, erasing the keys which
  are missing at that level.
- Add LabeledArray::getRow by label, and tests for the above.

Without a mapping the plain options are unchanged.