Eliminate more spelling differences between American and British English

[lgoettgens]

Follow-up to #3367 with even more things I found.

This introduces two new deprecations, namely:

• labelled_matrix_formatted -> labeled_matrix_formatted
• recognise -> recognize (in the SolveRadical submodule)

Can someone with access to the book please check, if these deprecations are an issue?

[joschmitt]

The functions are not used in the book. But a general question: I understand that we want to have consistency with function names, but is the policy now to enforce American spelling in the documentation too?

[fingolfin]

I am fine with that, but if this is now the standard, we should document it at such, too, if we don't already (not a blocker for this PR, though)

[lgoettgens]

If we want to have these two function renamings in 1.0, please go ahead with merging.