Add new OMERO.matlab function to update an original file with new content
Update WriteData example to illustrate new updateOriginalFile function
Add wrapper function to update a file annotation with new content

updateFileAnnotation() allows the user to update the file content of an
existing annotation. Optionally, the description and the namespace of the file
annotations can be updated as well using parameter/value pairs.
Update WriteData example to use the new update function
Use getHash() method to retrieve server-side file checksum
Merge pull request #1350 from sbesson/rebased/develop/matlab_updateoriginalfile

OMERO.matlab: add functions to update file annotations (rebased onto develop)