Handle web+ftb uploads

[hexylena]

Based on some comments on IRC this morning, bioblend won't upload files larger than 2GB. Not surprising.

We should check file size, upload via web if possible, and if larger than that, upload via FTP (will require user interaction for login details) in order to make the user experience more seamless for put() commands.

[hexylena]

For my future reference, uploading from FTP looks like:

inputs = {
    "files_0|ftp_files":"path/to/file",
    "dbkey":"?",
    "file_type":"auto",
    "files_0|type":"upload_dataset",
    "files_0|space_to_tab": None,
    "files_0|to_posix_lines":"Yes"
}