Support macro \cacheMeCode from robust-externalize

[jlelong]

This is a follow-up on #79 #77.

This PR adds support for \cacheMeCode[options]{code}. Both the content of [] and {} can span over several lines.

@dflvunoooooo @tobiasBora Currently the code part is considered as verbatim. Would it make sense to support embedded language and if so how can it be inferred from the optional argument?

[tobiasBora]

Thanks a lot! So a few remarks:

• I use the convention that environments start with upper case letter and command with lower case letters,
• \CacheMe (or rather \cacheMe) is morally the command version of \begin{CacheMe}, that we decided to keep in LaTeX form as it actually parses the code as LaTeX (removing %…), so I guess it would make sense to do the same for \cacheMe
• \cacheMeCode[preset options]{code} is indeed the equivalent of \begin{CacheMeCode}{preset options}code\end{CacheMeCode} (or rather will, I wrote it recently and I'll push it soonish once I finish working on a nicer way to work with python & sagemath). But the idea is exactly the same : you can parse the language exactly like in CacheMeCode to print it accordingly.

[jlelong]

Thanks for the explanations. I fixed the macro name to only consider \cacheMeCode. As for the CacheMe environment, the standard LaTeX grammar can already handle the macro \cacheMe.

I will add the recognition of embedded languages for \cacheMeCode.