Add imports check to travis build

This will compile a list of Python files in OmeroWeb and try to import
them to discover if any file has imports that do not work.

flake8 does not detect non-working imports.
Move import check after build step
Add pythonpath for django requirement
Merge branch 'develop' into travis-omeroweb-imports-check

Conflicts:
	components/tools/travis-build
Install pytest via pip for import check
Log imports being checked to output
Convert SessionControl._parse_conn into a static method
Add unit tests for static SessionsControl._parse_conn() method
Use group naming for clarity in _parse_conn and add docstring
Extend unit tests to cover empty string input
Add tests for connection string parsing with wild users and bad ports

- Increase stringency of regular expression to match up to 5 digits for ports
- Test connection string with user containing both : and @ characters
- Add test with invalid port and check the port is parsed with the server name
Update develop submodules

Repository: openmicroscopy/openmicroscopy
Already up-to-date.

Repository: openmicroscopy/bioformats
Updating 9f1a93b..f247b30
Merged PRs (fast-forward):
  # PR 1055 rleigh-dundee 'Fix up Bio-Formats POMs (rebased)'
  # PR 1063 melissalinkert 'Micromanager fixes (rebased onto develop)'
  # PR 1065 sbesson 'Update auto-generated documentation'

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

Repository: openmicroscopy/ome-documentation
Updating 44094aa..be161c6
Merged PRs (fast-forward):
  # PR 755 rleigh-dundee 'Search.txt: Correct use of unicode quotes'
  # PR 745 sbesson 'OMERO.matlab improvements (rebased onto develop)'
  # PR 754 sbesson 'Document new integration jobs'
  # PR 752 rleigh-dundee 'ant: Support API doc generation'

Generated by OMERO-5.1-latest-submods#90 (http://ci.openmicroscopy.org/job/OMERO-5.1-latest-submods/90/)
Merge pull request #2350 from knabar/travis-omeroweb-imports-check

Travis check for Python imports in OmeroWeb
Merge pull request #2374 from snoopycrimecop/merge/develop/submodules

Update develop submodules (periodic merge)
Merge pull request #2388 from sbesson/rebased/develop/parse_conn_tests

Add unit tests for CLI connection string parser (rebased onto develop)