Update SignName.vue first name & last name fields

[christina-ml]

Update the SignName component to have a first name and last name field. For issue #521 Update front-end to prepare for Stripe update

[paramsiddharth]

src/components/SignName.vue

server/routes/api/lob.js

[christina-ml]

Updated SignName component with requested changes.

[christina-ml]

Updated SignName component with requested changes. Formatted files with prettier.