Allow uploading files from streams

I have:

* made it so we can pass an InputStream to upload a file (no longer forced to upload a file from the disk)
* removed code duplication
* used Apache Commons IO to read the file, thus removing unnecessary code

Please merge https://github.com/asposeforcloud/Aspose_Cloud_SDK_For_Java/pull/4 before as the StringUtils class is part of Maven dependencies.