plugin invocation: explicit access to originating tiddler

[FND]

When evaluating JavaScript? code from a systemConfig tiddler, there should be an explicit contract for the the respective tiddler object to be passed in (e.g. by wrapping the invocation in a closure).

While this is already possible using the tiddler object from the parent scope (loadPlugins), that seems accidental and fairly brittle (e.g. if there is a local tiddler variable).

[FND]

Example use case: changeset:8843

[FND]

loadPlugins should be refactored to call an invokePlugin function.

[MartinBudden]

It's not worth changing the current contract with plugins.