ND2: reset series count before allocating offset array

This prevents extra memory from being used if the series count was too
high.  See http://lists.openmicroscopy.org.uk/pipermail/ome-users/2014-September/004699.html
Leica LIF: fix support for new files with 0 padding

Fixes #12144
Zeiss CZI: fix dimension calculations when expected planes are missing

See #12556.
Zeiss CZI: make sure pixel buffer is cleared

This prevents blank planes from containing garbage data.
Zeiss CZI: flag all files as being pixels files

This prevents pixel data from being accidentally included on the
companion file list.
DICOM: also use the pixel sign tag to detect the pixel type

Closes #12568.
merge dev_5_0 -Dorg -Ssuccess-only: PR 1398 (ND2: reset series count before allocating offset array (rebased onto dev_5_0))
merge dev_5_0 -Dorg -Ssuccess-only: PR 1399 (Leica LIF: fix support for new files with 0 padding (rebased onto dev_5_0))
merge dev_5_0 -Dorg -Ssuccess-only: PR 1400 (Zeiss CZI: fix dimension calculations when expected planes are missing (rebased onto dev_5_0))
merge dev_5_0 -Dorg -Ssuccess-only: PR 1401 (DICOM: also use the pixel sign tag to detect the pixel type (rebased onto dev_5_0))
merge dev_5_0 -Dorg -Ssuccess-only

Repository: openmicroscopy/bioformats
Excluded PRs:
  # PR 1393 melissalinkert 'Update version numbers to 5.0.6' (label: exclude)
Updating 440626c..dadf598
Previously merged:
  # PR 1392 hflynn 'Fix Analyze 7.5 specification link (rebased onto dev_5_0)'
  # PR 1380 hflynn 'Replace BigTiff sample link (rebased onto dev_5_0)'
  # PR 1372 sbesson 'Document usage of setSeries() and getIndex() in MATLAB documentation (rebased onto dev_5_0)'
  # PR 1367 hflynn 'Adding external PR guidance to CONTRIBUTING.md (rebased onto dev_5_0)'

Merged PRs:
  # PR 1398 melissalinkert 'ND2: reset series count before allocating offset array (rebased onto dev_5_0)'
  # PR 1399 melissalinkert 'Leica LIF: fix support for new files with 0 padding (rebased onto dev_5_0)'
  # PR 1400 melissalinkert 'Zeiss CZI: fix dimension calculations when expected planes are missing (rebased onto dev_5_0)'
  # PR 1401 melissalinkert 'DICOM: also use the pixel sign tag to detect the pixel type (rebased onto dev_5_0)'

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