[Geany] New request for "Save as"

[jerome]

Hello,

I've a new request for you :)

When I use "Save as", I wish that save as a new file but open this new 
file in new tab and not replace currently file.

Ex :
I have two file opened : "[]" represent a tab and "*" the selected file.
[File1.test*] [File2.test]

Also, I save as a new file. I enter a name (ex: File3.test) and 
validate. A new tab is opened:
[File1.test] [File2.test] [File3.test*]

Content of file File3.test is the same as File1.test.

I suppose this is a good idea, for me it is :D

Thank you.