MassSpectrumOnDisk Functionality

[dsammour]

• Added a new MassSpectrumOnDisk class which inherits AbstractMassObject class and whose Mass and Intensity slots are of "matter::matter_vec" class.
• The Mass and Intensity slots of AbstractMassObject have a classUnion type of "numeric" and "matter_vec".
• Edited methods of AbstractMassObject to comply with MassSpectrumOnDisk objects.
• trimming and subsetting create in-memory MassSpectrum objects when called on the new type.
• Edited documentation accordingly.

[dsammour]

Thanks for your reply/review Sebastian.

I see your point on removing the dependency on matter. As you showed in your onDiskVec example, we just need to write and read one vector at a time. The onDiskVec should have path, offset, size and length slots to account for imzML datatype. However, if we do this, we'll lose the meta data and length method available in a matter_vec object and therefore, every time we need to do some check on length, etc. the whole vector has to be read. Is there a good solution for that for onDiskVec?