Simplify data structure

A lot of data structures are rather complicated, and also quite nested. This has two undesirable effect :

• It complicates the code base, making it harder to reason with
• It hinders performance, though we (for now) cannot tell by how much

Since each undesirable interaction that leads to complicated data structure will have it's own specific, and therefore likely it's own solution, the details of those will be discussed in their own child issue.

Priority (subject to change)

Here is an estimation of what issue would yield the most gain, performance wise :

• issue #16 is the most clear cut, as the structure of the record has a direct significant impact on I/O
• issue #17 (closed) and #8 are probably tied, having both a small impact on I/O and a good impact on CPU usage
• issue #11 and #10 (closed) are likely the most insignificant changes, both affecting only memory and CPU performance