Merge pull request #65 in TPSH/ckanext-odsh from dev to master

* commit 'a706fda1':
  adds missing except
  adds correct error handling to logging of API requests
  fixes bug during logging of requests
  allows spatial_url_temp as alias for spatial_uri_temp
  adds posibility to log POST request to API, flag: ckanext.odsh.log_api_requests
  minor changes
  adds tests for validate_extra_groups if groups in extras from API
  further refactoring of validate_extra_groups
  refactors validate_extra_groups
  adds unittests for validate_extra_groups and starts refactoring
  adds unit tests for validate_licenseAttributionByText
  clears proxy after download
  implements upload of linked resources
  makes license attribution optional
  makes license attribution optional
  zwischenstand
  zwischenstand