New renal classification

[nicolevasilevsky]

Per the call today with renal experts, we decided we should reclassify the kidney disease terms in Mondo per the Brenner and Rector's The Kidney.

@sabrinatoro could you please do the following:

1. see if you can get an ebook of this book at the CU library (I haven't used the library yet myself!)
2. review the top level classifications of kidney diseases per the table of contents (like we did for Harrison's). Map the classes to existing Mondo terms (I suggest doing this in a spreadsheet)
3. Review/skim the chapters and note which diseases are classified under each top level class. Map existing classes to Mondo IDs.
4. before we make any changes in Mondo, we should review this with the kidney experts - we should set up a call with them
5. The kidney experts may have proposed name changes. We should include Ada on the follow up call to discuss this too.
6. Once agreed upon, we should implement this new hierarchy in Mondo.

cc @pnrobinson @cmungall @mellybelly