PATH for context file open

[DavidG]

Allow you to specify a PATH (through an environment variable) that will be searched for files that are opened using the context menu when editing.
An environment variable is often available to specify the search path so it is the ENVIRONMENT VARIABLE that needs to be specifiable not the actual path.

Current situation is:
When you right click on a file name you have the option to open the file.
As far as I can see there is no facility to provide an environment variable or explicit PATH so it will only open a file that is in the current directory.
Currently I think the context menu comes up when you have the syntax "include xxxx". This could be made for flexible as well - just in case!