TESTBOX-354 - bind utility functions with closure to currently executing spec

[sfeldkamp]

Fixes an error that occurred when using request.testbox.debug or request.testbox.clearDebugBuffer.

Fixes a bug that would cause debug messages to appear in only the first suite to be loaded.

Lets request.testbox.debug have it's label calculated automatically just as debug (in a spec) does.

https://ortussolutions.atlassian.net/browse/TESTBOX-354