cpp: xerces: Correct clang++ warnings in entity resolver
cpp: xerces: Update API documentation
Use __import__ for generateDS to handle FS case issues

While mounting the source tree from an OSX 10.10 host
over boot2docker to an Ubuntu container, Bio-Formats
builds failed with:

```
Traceback (most recent call last):
  File "./xsd-fu", line 45, in <module>
    from ome.modeltools import generateds
  File "/opt/tmp/components/bioformats/components/xsd-fu/python/ome/modeltools/generateds.py", line 6, in <module>
    from generateDS.generateDS import XschemaHandler, set_type_constants
  File "/opt/tmp/components/bioformats/components/xsd-fu/python/ome/modeltools/generateDS.py", line 6, in <module>
    from generateDS.generateDS import XschemaHandler, set_type_constants
ImportError: No module named generateDS
```

since there is a case-insensitive clash between our
ome.model.generateds (imported relatively) and
generateDS.generateDS (imported absolutely).
Generic fixes : Code cleanup
Merge pull request #1451 from melissalinkert/im3-metadata

Fix im3 metadata
merge develop -Dorg -Ssuccess-only: PR 1407 (TIFF: fix plane count calculation for pyramids with multiple planes)
merge develop -Dorg -Ssuccess-only: PR 1420 (Updating samples and adding units samples)
merge develop -Dorg -Ssuccess-only: PR 1431 (Specification: Add XML catalogues for released schemas)
merge develop -Dorg -Ssuccess-only: PR 1441 (Fix OME-XML BinData decoding)
merge develop -Dorg -Ssuccess-only: PR 1442 (Update roi handler)
merge develop -Dorg -Ssuccess-only: PR 1448 (Metamorph: allow both sanitized and unsanitized delimiters)
merge develop -Dorg -Ssuccess-only: PR 1450 (Reduce memory needed to open PNG images)
merge develop -Dorg -Ssuccess-only: PR 1452 (Use __import__ for generateDS to handle FS case issues)
merge develop -Dorg -Ssuccess-only

Repository: openmicroscopy/bioformats
Excluded PRs:
  # PR 1426 qidane 'Initial Rendering Definitions schema' (exclude comment)
  # PR 1444 snoopycrimecop 'Update auto-generated documentation' (status: failure)
  # PR 1437 stelfrich 'Changed handling of empty series names in ND2 files' (user: stelfrich)
  # PR 1443 joshmoore 'Genshi ZIP' (label: exclude)
  # PR 1177 rleigh-dundee 'specification: Add metadata for HDF5 embedding' (exclude comment)
  # PR 1365 ctrueden 'PrairieView 5.2 fixes and improvements' (label: exclude)
  # PR 857 melissalinkert 'Initial support for Zeiss .lms files' (label: exclude)
  # PR 1366 ctrueden 'Miscellaneous cleanup' (label: exclude)
  # PR 1453 jburel 'Fix mock object to match changes from int to double for channel' (status: error)
  # PR 858 melissalinkert 'Initial support for Veeco AFM data' (label: exclude)
  # PR 1381 melissalinkert 'Parse physical pixel sizes from CellSens .vsi datasets' (label: exclude)
  # PR 1309 melissalinkert 'Allow tile-based access of large JPEG-2000 images' (exclude comment)
  # PR 1015 qidane 'Messy binary' (exclude comment)
  # PR 1161 sommerc 'Initial CellH5 Reader class' (user: sommerc)
  # PR 1435 joshmoore 'Ordered MapPairs implementation' (label: breaking)
Updating b3962bd..e7ddc61
Previously merged:
  # PR 1451 melissalinkert 'Fix im3 metadata'

Merged PRs:
  # PR 1407 melissalinkert 'TIFF: fix plane count calculation for pyramids with multiple planes'
  # PR 1420 qidane 'Updating samples and adding units samples'
  # PR 1431 rleigh-dundee 'Specification: Add XML catalogues for released schemas'
  # PR 1441 melissalinkert 'Fix OME-XML BinData decoding'
  # PR 1442 bramalingam 'Update roi handler'
  # PR 1448 melissalinkert 'Metamorph: allow both sanitized and unsanitized delimiters'
  # PR 1450 melissalinkert 'Reduce memory needed to open PNG images'
  # PR 1452 joshmoore 'Use __import__ for generateDS to handle FS case issues'

Generated by OME-5.1-merge-push#618 (http://ci.openmicroscopy.org/job/OME-5.1-merge-push/618/)