Add MeV Analysis file as a file type for bioassay sets

[Nicklas Nordborg]

The scenario is this. A users uses the MeV extension to export and download data to MeV. In MeV some analysis steps are done and saved as a MeV analysis file. The file is uploaded to BASE and the Manual transform plug-in is used to register the work done in MeV as a new bioassay set. The analysis file is attached to the new bioassay set and can later be downloaded and opened in MeV in the same way as as the original data.

This ticket is a preparation for a more automated procedure that should implement a "Save to BASE" function directly in MeV.