Make FileDelegate WRITE FileOp useful

[wwelling]

Currently the FileDelegate WRITE is not used in any workflow and simply writes each input variable to a line in a file. This is not useful. To address a requirement of TAMULib/fw-registry#327 we should have the Java FileDelegate specify a target input variable to write to a file. The target variable as a list should be iterated and write an entry per line until further specifications are provided.