#1 Bibtex-style macro usage/expansion

[Lutz Ißler]

Bibtex provides definition and expansion of macro
strings, ie. "jan" expands to "January".

The Biber should support a more sophisticated version
of that. For example, one can define a macro string
named "jan". These strings can be used anywhere in the
bibliography.

Additionally, one can define several "named expansion
sets" for the macro strings. For example, one can
define a expansion set named "German" and one named
"English". The "German" set expands the macro "jan" to
"Januar", and the "English" set expands it to "January".

I think the expansion should occur when exporting the
file to Bibtex or other formats. There should be a
possibility to select a default expansion set, and a
way to explicitly select one for each export.