Updated and OneDrive provider, isReachable() with error

• General

  • Source breaking change: isReachable() returns error encountered in addition to success.
  • Optimizations and refactorings
  • Added Concepts and design document.
  • Fixed error description for file provider errors.
  • Known Issue: Progress for thumbnail and properties does not work yet.

• OneDrive

  • OneDrive provider now works with new Microsoft Graph API perfectly
  • Unlimited uploading

• iCloud

  • iCloud overwrite parameter ignored when uploading file (#82)

• WebDAV

  • searchFiles() "including" param was being ignored.