added comment about project version

services/web/app/coffee/models/Project.coffee

@@ -22,7 +22,7 @@ ProjectSchema = new Schema
 	readOnly_refs     :   [ type:ObjectId, ref:'User' ]
 	rootDoc_id        :   {type: ObjectId}
 	rootFolder        :   [FolderSchema]
-	version           :   {type: Number}
+	version           :   {type: Number} # incremented for every change in the project structure (folders and filenames)
 	publicAccesLevel  :   {type: String, default: 'private'}
 	compiler          :   {type:String, default:'pdflatex'}
 	spellCheckLanguage :   {type:String, default:'en'}