Use first and last name fields

[cecilia-donnelly]

From a user in "SWOP Database 09142015 Observations":

"Note: Discussed, please add first name and last name entry fields instead of having one entry field for participant name."

Which is to say, undo the changes from #86.

[nttaylor]

This change is more difficult than it may have seemed at first, given that the dynamically filled tables (e.g., the sign-in sheet) currently do auto-complete matching against both first and last names. This matching would still work in a scheme with separate first and last name columns -- a user who is editing either first or last name could make a selection from the auto-complete options, which would then populate both fields -- but implementing this would take time. There would be further layout complications for dynamically generated tables with two name columns such as determining the placement for the profile link that appears next to the name when in read-only mode.