Dataset adding/removing samples improvements

[gtarcea]

• "+Add existing samples" button not working
• the "Edit sample" popup is a nice display of information
• the "Edit sample" popup seems to be using test data that is not from my project and I can't for example remove a process. is there a way to show this without it being a popup?
• removing a sample doesn't seem to propagate to removing associated files and I'm assuming it also doesn't propogate to associated processes
• this tab could use some descriptive text along the lines of: "Edit which samples are included in the dataset. <Explain rules of whether adding / removing a sample propogates to adding / removing files and processes, measurements, etc.>. Click on a particular sample to see exactly which files and processes are associated with the sample."
• adding/removing attribute sets / measurements: let's assume first iteration doesn't let you customize this, but might be part of the "edit samples" popup? other method to edit that?