Open PDF from Actor/Item popup menu

[farling42]

Add an option to the popup menu in the sidebar for Actors and Items, which will open a PDF page that has been preconfigured for the type of the Actor or Item.

• [ ] A configuration mapping table to define which PDF Code to use for each type of Actor and Item defined for the world's game system.
• [ ] Create a function getPdfForCode with code that is currently hidden inside openPDFByCode, to use with the new function.
• [ ] Work out how to add an additional entry to the Actor/Item popup.
• [ ] The menu entry should only appear if the Actor/Item has a type which a PDF Code configured for it.

[farling42]

Version 0.15.0 adds additional module configuration options to specify the PDFCode of the PDF to be opened for each type of Actor and/or Item. A new entry will appear in the context menu for the Actor and Item sidebars which will open the selected item in the PDF page with the configured PDF code (if no PDF code is configured for the type of Actor/Item, then the menu option will not appear).