Fix edge case with nested choices. Fixes #560

When the set of choices is a list containing a named vector of length 1,
choicesWithNames would return the wrong result.
no need to use wrap = FALSE for roxygen2 now
fixes #557: choicesWithNames() turns a character vector to a list, which is no longer appropriate as a column in data.frame()
bump version
a typo in the news for 0.10.1