Alternative to Vuetify layout (v-layout, v-flex)

[MatthewGidcomb]

v-layout is, at least the way we've used it, a flexbox-based 12-column grid implementation (and we commonly use < 12 columns, leaving some gutter on the right) It is used in three components:

• AddNewVenue (wrapper around the subset of submission form fields for creating a new venue
• SubmissionForm (quite heavily; it's the basis of pretty much the entire layout)
• contact page form (similar to submission form, but so simple in this case it can easily be replaced with a max-width)

We need a non-Vuetify replacement. Fortunately, it's just flex; this is straightforward.