First pass of EUtils ⚠️ (not ready for merge) ⚠️

This ports over all the code that we had in cogent.db, I have explicitly left
out the submodules related to RFam and PDB. I've also ported over the super
awesome tutorial that exercises a lot of the functionality in this module.

The few things that I can think of for immediate improvements are:

- Unit Tests
- Organization (there are far too many private functions).

For now I want to see how we are doing in coverage for these modules and make
sure that everything is Kosher.

It would be great if someone could take a pass at it.
Change:

* For example, in the unlikely event that I want NCBI to contact me instead of Mike if something goes wrong with my script, I can achieve that as follows:*

to:

*For example, if I want NCBI to contact me if something goes wrong with my script, I can achieve that as follows:*