Added basic metadata for MALDI-TOF MS spectra

[Mailaender]

This is a followup to #911 which adds some metadata fields commonly found in data files.

[eselmeister]

I would recommend to move the class ExtendedMassSpectrumHeaderUI.java to the package:

org.eclipse.chemclipse.ux.extension.xxd.ui.swt

Normally, scans of a chromatogram don't need variables like File or Header values. Hence, I would recommend to introduce a new interface on top of IVendorMassSpectrum probably name it IVendorMassSpectrumTOF

IVendorMassSpectrumTOF extends IVendorMassSpectrum

which contains the header values and the file member. Regarding the header values, have a look at the chromatogram. It implements IMeasurementInfo, which stores the header values as a map and thus is easily extensible. Specific header values like Date or Operator are pre-defined.

The TOF specific classes could look like this:

public class VendorMassSpectrumTOF extends AbstractVendorMassSpectrumTOF {...}
public abstract class AbstractVendorMassSpectrumTOF extends AbstractVendorMassSpectrum implements IVendorMassSpectrumTOF {...}

If TOF specific functionality is required, an instanceof could be used. Otherwise, the basic OpenChrom functionality can simply be used.

[Mailaender]

I thought IMassSpectrum was already for single MS spectra. Indeed empty fields at this magnitude are an avoidable performance problem. I refactored it as suggested.