Refactor step 1: energy calibration

[woutdenolf]

To refactor:

• Simplify the fitLine and curveCalibration groups to get more or less the 4 plots above
• Automate peak detection: get list of emission energies from a database (e.g. pymca) and use estimation of zero and gain
• External links to the raw data?
• improve the calibCoeffs results structure