Improved gdrive allDocs test to check return value.

various conditions optimized
added compliance with future tests.

added error message when giving non-boolean value
for "trashed" value at creation of gdrive storage.

to not receive corrupted files

when attempting to remove an inexistent document.

added comments in dropboxstorage.js about the Dropbox API limitations.

updated dropboxstorage.tests.js to suit to previous changes in dropboxstorage.js

Never build URL by concatenating strings, as it does not correctly handle escape.

Remove useless requests which will not prevent raise condition.

allowing to choose between "dropbox" (access to full dropbox account)
and "sandbox" (cannot access files not created by the jio application)
mode.

of putattachment method (150MB limit)

works with the new dropbox API.
dropbox storage redesigned to have the same behavior as DAV storage.

This storage will transparently compress getAttachment/putAttachment results.
Only text, json, xml mme type are compressed.

Thanks to Lucas Parsy.

Activate it by adding the 'repair_attachment' parameter in the storage description.
Then, call the repair method.

This was just a prototype, which has been replaced by the replicatestorage.

Configure the storage with the conflict_handling parameter value:
   0: (default): no resolution (ie, throw an Error)
   1: keep the local state
      (overwrites the remote document with local content)
      (delete remote document if local is deleted)
   2: keep the remote state
      (overwrites the local document with remote content)
      (delete local document if remote is deleted)
   3: keep both copies (leave documents untouched, no signature update)

This shows how to use localstorage, indexedDB, dav, replicate.

This allow to not check the document in the second step of synchro.

Array parameters are converted to multiple FormData.append calls.