File list merge cases

[derhofbauer]

When walking through local and server file list and determining what to do a few cases have to be handled:

• File/Folder exists locally but not on server: Upload file/create folder on server
• File/Folder exists on server but not locally: Download file/create folder locally
• File exists on both ends but is newer* locally: upload file overwriting file on server
• File exists on both ends but is newer* on server: download file overwriting local file
• File exists in both ends and has conflicting changes: figure out whether Dropbox handles this case

*) "newer" in this cases means edited more recently