Minor a11y changes to views

Fixed a small # of missing alt attributes. Images did not convey any information and/or other text adjacent to the image was sufficient, so they were given empty alts.

Changed an empty TH element into TDs. Empty TH elements may be confusing for screen reader users

Changed tabindex="1" to tabindex="0". Tabindex values > 0 become an explicit tab stop. IOW, because the tooltips had tabindex="1" it would take the first position in the tab order.  But, giving it tabindex="0" allows it to take its "natural"  spot in the tab order.

For views/account/editor.html - each field had two labels: 1 intended to be the label and the 2nd intending to be a description.    The problem with using two `label` elements is that screen readers will only read the first one.  IOW, the description isn't read.   The solution: use a `div` with an `id` that can be referenced with `aria-describedby`.  This will reliably allow ARIA-supporting assistive technologies to read the description.


NOTE ON THIS PR: I've not verified that there aren't any (visually) breaking changes. There shouldn't be, because the class names remain unchanged.