Switch to using Google Drive SDK, closes #2047
Setting Redirect URI is not required here
Prepare for #2013 fix
Fix constant in last commit
Include 3rdparty Google Drive SDK 0.6.2
Fix require_once for 3rdparty in google ajax frontend
Return null if file size is negative for WebDAV, fix #2013
Implement hasUpdated() to watch for changes on Google Drive side
substr storage id to prevent problems with storing the change id in appconfig
Fix 'most' Google Drive tests
Remove root option from Google Drive storage, because it is only used for testing and we have our own empty Google account for testing
Merge pull request #4306 from owncloud/stable5-googledrive

[Stable5] backport  Google Drive SDK