rcx-tk: add description and change label of output based on parameter etc.

[hechth]

The tool is currently lacking a description tag (https://docs.galaxyproject.org/en/latest/dev/schema.html#tool-description) which should briefly describe what the tool does or how it can be used.

Also, currently, all tool outputs are just being given the label "processed data" which is not helpful. Depending on which mode is chosen, it should be something like "Parsed alkane file from data xzy" or "Parsed metadata table from data xzy".

Additionally, I think the tool also lacks a comprehensive help text.

[acquayefrank]

@hechth I am working on this, but I need a bit more context. Could you kindly explain this a bit further?