Add calibration pages from the old sphinx docs.

Code/Mantid/docs/source/api/python/index.rst

.../Mantid/docs/source/api/python/techniques/calibration.rst

...urce/api/python/techniques/calibration_implementation.rst

Code/Mantid/docs/source/images/calibrateB2Window.png

...s/source/images/calibrateChangeMarginAndExpectedValue.png

Code/Mantid/docs/source/images/calibratePlotFittedData.png

Code/Mantid/docs/source/images/calibratedCurrentMerlin.png

Code/Mantid/docs/source/images/calibratedMantidMerlin.png

Code/Mantid/docs/source/images/outputOfMinimalInput.png

Code/Mantid/docs/source/images/plotingPeaksDifference.png