Small LaTeX adjustments

[ScriptRaccoon]

1. All := have been replaced with \coloneqq. The vertical spacing is better. Same with the mirrored \eqqcolon.
2. The morphism declarations f \colon X \to Y (written by one contributor) and f : X \to Y (written in all other cases so far) have been unified: we only use f : X \to Y. Even though this is considered wrong, I must say that I never found any of these arguments compelling and also I like the spacing of the : much more.
3. A couple of \simeq ($\simeq$) have been replaced with \cong. The symbol $\simeq$ should only be used for equivalences that are no isomorphisms.
4. Add macros for \mathfrak{p} and \mathfrak{m}.
5. other minor stuff