update .gitignore to ignore IDEA project files
Adds updateFileList method to TransferManager. updateDirectory is delegated to updateFileList method.
adds check, if all files in fileList are actual files and not directories, in order for them to be uploaded.
Adds more comments
Adds null check for empty file list.
Uses default behavior as for an empty fileList and set TransferState to Completed
Updates Comments
Merge pull request #47 from weitzj/feature/transferManagerFileListUpload

Adds public uploadFileList method to TransferManager for use-case of ignore/exclude lists