Add support for OMERO_SESSION_DIR environement variable

With this commit, having OMERO_SESSION_DIR set should allow all CLI commands
to default to another sessions directory than the default one.
Suppress the session-dir argument help and expose the envvar
Fix extended help to use OMERO_SESSIONS_DIR
Add unit tests for sessions store directory
Fix OMERO_SESSION_DIR help indentation
Merge remote-tracking branch 'origin/develop' into omero_session_dir

Conflicts:
	components/tools/OmeroPy/src/omero/cli.py
Fix flake8 warnings
Invert order of optional session arguments and environment variables
Merge pull request #3032 from sbesson/omero_session_dir

CLI: add OMERO_SESSION_DIR environment variable
merge develop -Dnone -Ibreaking -Eexclude -Ssuccess-only: PR 3033 (Float re)
merge develop -Dnone -Ibreaking -Eexclude -Ssuccess-only

Repository: openmicroscopy/openmicroscopy
Excluded PRs:
  # PR 2585 aleksandra-tarkowska 'making time_zone and first_day_of_week configurable' (exclude comment)
  # PR 3043 ximenesuk 'Flake8 various files under OmeroPy (part 2)' (exclude comment)
  # PR 3037 joshmoore 'Group sudo' (user: joshmoore)
  # PR 2182 joshmoore 'Read only flag' (user: joshmoore)
  # PR 3040 ximenesuk 'Flake8 various files under OmeroPy' (user: ximenesuk)
  # PR 3039 will-moore 'Float rendering web' (user: will-moore)
  # PR 2979 will-moore 'Thumbnail cache busting' (user: will-moore)
  # PR 3000 jballanc 'Update artifacts for Lucene, Hibernate, and Spring' (user: jballanc)
  # PR 3042 will-moore 'Download dataset project' (user: will-moore)
  # PR 2412 qidane 'Extra annotations' (status: failure)
  # PR 3036 snoopycrimecop 'Update develop submodules' (user: snoopycrimecop)
  # PR 3046 aleksandra-tarkowska 'updating auto generated text' (user: aleksandra-tarkowska)
  # PR 3031 bramalingam 'Permissions test all' (user: bramalingam)
  # PR 3016 dpwrussell 'Jquery update migration (Part 1 of n)' (user: dpwrussell)
  # PR 3035 sbesson 'Add local table of contents to auto-generated configuration page' (user: sbesson)
  # PR 3028 sbesson 'Matlab getPlane efficiency' (user: sbesson)
  # PR 2895 dominikl 'Reload groups after users added/removed' (user: dominikl)
  # PR 2987 rleigh-dundee 'travis: Build with Oracle JDK 8' (user: rleigh-dundee)
  # PR 2985 will-moore 'Download preserves directories of original files' (user: will-moore)
  # PR 2363 dominikl 'Java Gateway API' (label: exclude)
  # PR 3029 rleigh-dundee 'OmeroCpp: Disable RMap and search tests' (user: rleigh-dundee)
Already up-to-date.

Merged PRs:
  # PR 3033 jburel 'Float re'

Repository: openmicroscopy/bioformats
Excluded PRs:
  # PR 1343 rleigh-dundee 'C++: TIFF pixel data read/write interfaces and skeleton implementation' (user: rleigh-dundee)
  # PR 1249 PremyslFiala 'ND2 - Bug fixes' (user: PremyslFiala)
  # PR 816 melissalinkert 'Add support for multi-channel Volocity Clipping datasets' (user: melissalinkert)
  # PR 1309 melissalinkert 'Allow tile-based access of large JPEG-2000 images' (exclude comment)
  # PR 1339 melissalinkert 'Amaris FlowSight' (user: melissalinkert)
  # PR 1177 rleigh-dundee 'specification: Add metadata for HDF5 embedding' (exclude comment)
  # PR 1154 melissalinkert 'Leica: prevent exception when linking EmissionFilter' (user: melissalinkert)
  # PR 1328 sbesson 'Use in-place caching by default in Memoizer' (user: sbesson)
  # PR 1296 melissalinkert 'Add test for getRequiredDirectories' (user: melissalinkert)
  # PR 1347 melissalinkert 'AIM: fix offset calculation for > 4GB files' (user: melissalinkert)
  # PR 1015 qidane 'Messy binary' (exclude comment)
  # PR 1265 qidane 'New units' (label: exclude)
  # PR 1315 LeeKamentsky 'IM3Reader for Perkin-Elmer Nuance' (user: LeeKamentsky)
  # PR 1302 sbesson 'Add branch-specific link for downloading the JAR file if unfound (rebased onto develop)' (user: sbesson)
  # PR 858 melissalinkert 'Initial support for Veeco AFM data' (user: melissalinkert)
  # PR 1161 sommerc 'Initial CellH5 Reader class' (user: sommerc)
  # PR 857 melissalinkert 'Initial support for Zeiss .lms files' (user: melissalinkert)
  # PR 1323 melissalinkert 'Add bit-level operations to RandomAccess{Input, Output}Stream' (user: melissalinkert)
Updating 0819d22..32c7be8
Previously merged:
  # PR 1342 joshmoore 'Catch all exceptions on loadMemo'
  # PR 1340 joshmoore 'kryo: update to 2.24.0 with shading changes (see #10852)'
  # PR 1331 rleigh-dundee 'C++: Add FormatWriter interface'
  # PR 1335 melissalinkert 'ND2: prevent NumberFormatExceptions when parsing text data (rebased onto develop)'
  # PR 1324 melissalinkert 'Deltavision: conditionally ignore stage position values of 0'
  # PR 1317 melissalinkert 'Gatan: fix physical dimension parsing when the Z size is missing'

Merged PRs:
  # PR 1054 qidane 'Additional annotation points throughout the model'

Repository: ome/scripts
Already up-to-date.

Repository: openmicroscopy/ome-documentation
Excluded PRs:
  # PR 991 aleksandra-tarkowska 'updating documentation to use new glosary' (user: aleksandra-tarkowska)
  # PR 973 hflynn 'Team workflow doc' (user: hflynn)
  # PR 990 kennethgillen 'for users who have compiled isapi_wsgi on x64' (user: kennethgillen)
  # PR 988 sbesson 'Property index' (user: sbesson)
  # PR 992 ximenesuk 'Add disk usage sections to cli pages.' (user: ximenesuk)
  # PR 989 sbesson 'Add paragraph about the store recycling while retrieving pixel data' (user: sbesson)
Updating 01a91b2..9dbefc4
Previously merged:
  # PR 986 sbesson 'Document usage of new OMERO_SESSION_DIR envvar for the CLI'
  # PR 987 snoopycrimecop 'Update auto-generated properties'
  # PR 984 aleksandra-tarkowska 'adding support for django directives'

Generated by OME-5.1-breaking-push#91 (http://ci.openmicroscopy.org/job/OME-5.1-breaking-push/91/)