[IDEA] Generalize the tree macro to support any field

[andjar]

Hi! Currently, the tree macro is only looking at the title field. It may be useful to generalize it to support an additional field parameter that defines the path. A tiddler with fields

title: /A/B/C
path1: /B/A/C
path2: /C/B/A

will then be placed at different location using the calls

<<tree prefix:"/">> // Defaults to title
<<tree prefix:"/" field:"path1">>
<<tree prefix:"/" field:"path2">>