Implement deserialization of dictionaries using primitives as keys

[Sprixitite]

Previously only worked with strings and would fail quietly if anything else was used (at least on net8.0, haven't checked other targets)

[coveralls]

coverage: 91.979% (+0.03%) from 91.945%
when pulling db9998b on Sprixitite:master
into a572b42 on SamboyCoding:master.

[Sprixitite]

With regards to deserializing generic dictionaries (as there currently is a naive serializer for them), it'll probably be necessary to expose an interface to convert objects -> keys and back

Another approach would be to serialize the keys and use the resulting string as the key? Would like to hear some thoughts on this

[SamboyCoding]

Content looks good but I would like to have a test to ensure it's valid and doesn't break in future.

[Sprixitite]

Good call on adding the tests, I evidently didn't check the floating point stuff well enough, some issues with the decimal point

I've removed double/float support from this PR as a result