Scent refactor part1

I'm interested in changing how the scentmap works, so I decided to learn how it works now. A lot of these changes are for readability, except for flag lookup separation: https://github.com/wormingdead/Cataclysm-DDA/commit/9314db29e5845dcb45bca258ec53b5850fec8946 and the temp_scent refactor 1 through 7.

As far as I can tell for the temp_scent refactor, there shouldn't be more precision loss than before due to integer division. I split up the simplifications to make it easier to follow, but let me know if I need to be even more explicit. (Or if I made a mistake!)

This is part 1 because I also fixed the sizes of the intermediate matrices, but that ended up being a big complicated commit. See last four commits in this branch: https://github.com/wormingdead/Cataclysm-DDA/compare/scent-refactor-part2. I will create a part2 PR if this one goes well.
I left it that way so that you can see that 4/5 of  the `squares_used` value (that has a maximum value of 90 and a minimum of 0) was being used and the final fifth was coming from a flat 90.

In other words, adding 1/5 of 90 plus 4/5 of a variable that is at most 90 gives you a maximum of 90 still, but the minimum is higher than the minimum of `squares_used`.