update tiddler macro to support data parameter.

[jdlrobson]

I believe with a small amount of code we can improve the tiddler macro to be more powerful.

This will be of use to TiddlyWeb development and also would lessen the need for using things such as the forEachTiddlerPlugin.

<<tiddler Template data:[[foo]]>>

Would print the tiddler with title "Template" however would do so in the context of the tiddler with title "foo"

If the text of "Template" was: <<view title> is the name of this tiddler.

Then the result of this macro call would be: foo is the name of this tiddler.

A tiddlywiki demonstrating the benefits and usage of this here:  http://www.jonrobson.me.uk/development/Tiddlers.html

I have attached a patch to Macros.js that provides this functionality.

[FND]

cf. #890

[MartinBudden]

Milestone 2.6.2 deleted

[cdent]

this seems to be plugin territory, not core territory?