Menu options to create various specialized new files - file templates

[szabgab]

In addition to the simple "New" menu option we might need to have a "new XYZ"

• New .pl file
• New .pm file
• etc...

These should immediately call save_as and use the appropriate template.

It can actually behave differently:

There is only a single "New saved file" option that calls save_as and then based on the extension we know which kind of file and which template to use.

One might want to add several different templates for .pm files so we might need to ask which template to use, before creating the file.