OMERO.matlab: add functions to update file annotations

Given an existing `FileAnnotation` with an `OriginalFile`, this PR 
- adds a function to update the `OriginalFile` with the content of a local file:

  ```
updateOriginalFile(session, originalFile, newFilePath);
```
- adds a function to update the `FileAnnotation` the the content of a local file and additionally update the description and the namespace:

  ```
fileAnnotation = updateFileAnnotation(session, fileAnnotation, newFilePath, 'description', 'new-description', 'namespace', 'new.namespace');
```
- update the `WriteData.m` example to illustrate this new functionality

/cc @mporter-gre