Rethink usage of currency

[soad003]

I think in the future tags should not be restricted on a currency basis. If addresses coincide on different chains it is highly likely that the address is held by the same party, thus it its sensible to propagate this tag to other currencies.

I propose to link restrictions when it comes to currencies, like that only tags of certain currencies can be included. Furthermore, i propose that queries against the tagstore should not be scoped by currency by default.