daily fluid balance implementation

[aegis301]

Several users already seem to have spoken about an implementation of fluid balance as a concept in mimic-code. This is a first kickoff for such an implementation on a daily fluid balance. Looking forward to your input!

[aegis301]

I noticed that I included too much values in the query, essentially including different units like mg and IE in the result. I fixed that to only include ml as unit of volume into the query. As state by the documentation on mimiciv_icu.inputevents in cases where there is an medication in mg and a volume these should be recorded both under the same orderid. E.g. 1000mg of Vancomycine in 100ml NaCl, there should be rows for both of them. By this query, I should be able to exclude the Vancomycine while keeping the NaCl bolus as is.