Header detection broken

[LumosX]

I'm using Mklauber's Tiddly Aliases plugin, and that allows one to add an aliases property to a tiddler. This script's header detection (line 89) fails when this property is present, as properties in the header are alphabetically ordered and "aliases" (or any other suitable property) ends up preceding one of the several ones the script is looking for.

Disabling the explicit header detection should be sufficient except for edge cases where the header is in a separate meta file. Perhaps checking whether a meta file exists is a better idea, and if not, assuming that the header must be present inside the .tid file.