Add some mathbb latex substitutions

[hayd]

It be great to have access to some of these mathbb symbols. These were not included due to "more latex code creeping" in (ie as mathbb{Z}).

A workaround to the having this more latex issue is to use the prefix: Bbb, i.e.\BbbZ. (In sense this is a standard; we are already have this for \BbbPi.

cc #6927 @stevengj

Note: it could be that font support is not that great for these symbols:

julia> println("\u2124")  # \BbbZ
ℤ

just looks like a Z to me in Source Code Pro (but maybe I should just use a better font).

[stevengj]

I'm not opposed to supporting \mathbb{Z} etcetera in the tab completions. I wanted to be more conservative in my initial patch, but now that we have some experience with this we can decide whether to include more.

Most of these substitutions are probably in unicode.xml already, but my import script stripped them out by the ismatch(r"^\\[A-Za-z]+$",L) rule. It would be easy to modify this to import a larger set of symbol substitutions.

[catawbasam]

Re font support: Deja Vu Sans Mono supports it and is freely available.

[hayd]

Perhaps adding "Springer" to the lookup tuple ("AMS", "IEEE", "mathlatex", "latex") would be a good/easy fix? (It gives \bbbz and more...)

[stevengj]

See #8044 for an alternative, which defines e.g. \BbbA for 𝔸.