Small changes to fix some initFile failures

zStep is always initialised as micrometer so no need to attempt unit conversion

checks that a single sublock exists when a cropped plane matches exactly a subblock region

Adds toString method to directory entry

…present as an orphan block at the end of the file.

- Fix mismatch between decompressed JPEGXR image dimension and subblock storedSize X & Y
- Proper reading of linescans (handling of subblocks containing multiple Z or Ts)
- Fix unit issue with linescans
- Avoids NPE issue when no scaling metadata is found
- adapts to PALM: make sure the data opens (downscaling can go below 1: superresolution)
- Make metadata reading robust with absence of some sub-blocks
- Correctly counts the number of channels, slices, and timepoints (they should always start at 0)
- be robust to absence of sub-directory segment
- There may be some information in slide previews that we do not want to keep. Hence a DummyMetadata is used when reading slide preview and macro images
Minor documentation and formatting changes

Attempt to close open file handles