Remove singular and plural version of functions for simplicity

[Huh]

As a future enhancement I would like to collapse build_vec_url and build_vec_urls into a single function. These are both internal functions and so there is no fear of the user being confused, but for simplicity I would like to collapse them even if it makes our code a little more difficult to read.

An alternative to one function is renaming the singular version so it does not follow the prefix convention and so is more hidden...but I would rather just make it go away.