dynamically write MerMEId version info to `mei:application`

[Peter Stadler]

mei:application/@version should be set automatically when creating a new file with the MerMEId. Right now it's getting the hard coded value from

MerMEId/forms/model/new_file.xml

Lines 35 to 37 in 210b08a

 <application version="2019"> 
    <name>MerMEId</name> 
 </application>