Extended search: do not cache operator options across corpora

[arildm]

The getOpts function in extendedCqpTerm builds operator options for the selected attribute. It is memoized, so the same attribute will yield the same operator options. However, different corpora may have different settings for the same attribute name. [Example needed.] Because of the memoizing, when changing corpus selection, the operator options will not change as they should.

It doesn't look to me like the memoizing is really needed. Try removing it. Otherwise, maybe use .cache of the memoized function to clear the cache when changing corpora. Or include corpus selection as an argument to cache by.