Provide support for more input-formats

[pverscha]

In order to improve intercompatibility of the Unipept Desktop application with other tools, we need to implement support for a variety of extra input formats that keep track of quantitative values for a sample.

Originally requested by a reviewer of our tool:

In many cases, the output provided by peptide identification tools in a typical metaproteomic (multisample) study consists in a list of all the peptides identified in the study (first column), followed by N columns containing the quantitative values measured for each peptide in N samples of the study (i.e. PSMs or area/intensity values).