Make column names meaningful upon project start

[trnstlntk]

Currently, when loading a new project with the Commons Extension, columns get generic names, ie Column 1 Column 2 etc.

It would be nicer if the columns had more meaningful names:

• File for the filename column
• Categories for the categories column, if the user requests this upon project start
• M-ids for the column with M-ids (same)

Other naming suggestions welcome :-)