(A11y severity 1) Autocomplete accessibility issues

Two (related) issues:

1. Screen reader users are not informed upon entering the "Share with" control that auto complete is enabled. Without being informed of autocomplete, users will continue to type a name and have no indication that options are being presented below for. This is a severe problem as users are required to select one of the options that appear below before they are permitted to navigate forward. Ensure that users are informed of auto complete.

2. When a screen reader navigates through the names below the textbox, the name of each user isn’t read. Instead the screen reader repeats the text typed by the user in the textbox for each user found. Enable the auto complete functionality so that it reads the names of selected users.
It might be better to abstract `hideResultsHolder` and `showResultsHolder` in functions, as we repeat the same code quite a bit now.