Fixes few HTML/CSS styles.
Move initialization of the blobstore provider from the provider's kotti_configure into Kotti itself.  This elimintaes the need to implement the same generic code in every provider over and over again.  It also allows to configure the blobstore with a single option only.  Update documentation accordingly.  Add YURL as a dependency / requirement.
Merge pull request #324 from disko/feature/blobstore_init

Move initialization of the blobstore provider from the provider's kotti_configure into Kotti itself
Require lingua 1.4 (1.5 and later fail on file ``tag_it.pt``).  [ci skip]
Update translation catalogs.  Complete German translation.  [ci skip]
Fix flaws in German translation.  [ci skip]
Add an icon to the "Apply changes" button in the user management screen.
- Define the ``IBlobStore`` interface.
- Add a ``kotti.blobstore`` setting.
- Add a ``delete_from_blobstore_providers`` event handler which notifies external storage providers.
- Make ``kotti.resources.File.data`` a hybrid attribute (with getter and setter).
- Add ``config`` fixture to list of arguments for some tests.
Refer to the event object.
Add additional note about class name case requirements.
PEP8.
Add a kotti-migrate-blobs console script.
Add sublime files to .gitignore.
Add documentation and fix mismatch of scipt name and help text.
Revert change that accidentally slipped in [bbfaa83].
Fix wrong interface definition.
Add tests.
Also test the ``delete_from_blobstore_providers`` event handler.
Add blobstorage topic to the docs index.  [ci skip]
Call db_flush in test.  Fix documentation / implementation mismatch.