Restructure samples, files for datasets 1

[glormph]

Samples can improve somewhat, this can be a first step:

• Change DB structure for samples (Bio - MS/genom/other - Channel/File - msprotocol)
• Current web view/frontend should cope with this, ideally not change frontend before next step, lots of work
• Dataset type field (MS, sequencing, image) to have as children LC/QC/Quant, RNA/WGS/... , microscopy
• Restrict datasets to have only files of their type

[glormph]

This issue is a bit vague on explaining. DB structure and frontend are under construction for this though as per #43.

The last two (dset field with children, and restrict to files of type) are less clear if we should go ahead with. Think a bit and then add the explanation here.