ET's essential geometric properties in detector's rest frame

detector locations, unit armvectors, detector tensors

	modified:   modules/ETdetector.py
	new file:   tests/ETdetector/Detector.py
Detector class describing location and detector tensors

Test written.
Detector class in ETdetector module is created by
an optional displacement vector of the centre of the ET triangle and
angles for an optional zyz-rotation of the ET triangle.

	modified:   modules/ETdetector.py
	modified:   tests/ETdetector/Detector.py
Give option to scale ET's armlength in ETdetector.Detector

This effects the methods

ETdetector.Detector.armlength()
ETdetector.Detector.loc()

	modified:   modules/ETdetector.py
Created is function to plot ET location and orientation

ETplot.plot_ETtriangle() takes a ETdetector.Detector object
and plots the ET triangle.

There is an option to centre ET to the origin, and to scale its
armlengths.

	modified:   modules/ETplot.py