title: google-apps-script have multiple scripts in one spreadsheet
body: <p>I have developed several general purpose script functions, for Google Spreadsheet apps.
  Currently I keep each function in an individual file on my lap-top. In order to include them
  into a spreadsheet, I only know of one way. </p>
  
  <p>Merge the individual function-files into one file. 
  Then copy and paste the data in the merged file into the
  spreadsheet's script editor, replacing the previous content.</p>
  
  <p>It would be nice if there was a way (e.g. using a "project") where
  the individual function files could be saved once and then I could 
  just reference those functions as needed in a new script. </p>
  
  <p>I don't know if there is such a possibility. I only see one node
  called "code" in the tree list of the spreadsheet content. </p>
  
  <p>Any help is appreciated.</p>