Allow editing file & folder names in-place (e.g. in "Save As" dialogs)

[xparq]

Some file/folder locations can't be edited directly in file-related dialogs (e.g. rendered audio filename, prj. folder etc.), only selected via the filesystem browser.

Sometimes (e.g. when only adding/changing a single character somewhere in the name would be all that's needed, or when copy-pasting paths from other applications etc.) it would be much simpler/quicker to allow typing directly in the file/folder name fields, instead of launching the browser (when the value is clicked), and doing the same thing there, but with several extra clicks.

(Incorrectly entered (nonexistent) paths would need to be handled later anyway, after clicking "OK" to start the actual save/export action.)