Introduce finitely tiny objects / finitely tiny generated categories

[MxmUrw]

Since using the usual definition of atoms/atomic categories (see #12), 𝐅𝐢𝐧𝐈𝐱 cannot be shown to be atomic, we introduce a suitable finite alternative.

Instead of requiring preservation of all colimits, we only require preservation of finite colimits. Furthermore, for the time being, we reduce the concept further, and only require the preservation of binary coproducts.

Here we use the name "tiny object" from [3] for this concept.

See (original concepts):

1. atomic category
2. atom
3. tiny object