refactor: De-tangle v-instructions directive completely

[toshify]

The v-instructions directive plugin is too entangled to the rest of the app. The litmus test is that it could not be provided as a npm package at this point. What needs to be done is:

• (PR#31) allow configuration of overlay style when setting up plugin
• allow overriding overlay style when using directive (v-instruction={audiourl, color})
• allow configuring instruction vuex state name, so that a dev can configure what vuex state name to use for toggling instructions mode
• have the plugin append the overlay rather than add it manually to
• make use of vuetify configurable and optional [We're no longer using Vuetify, we've switched to Ionic]

[toshify]

Some work was done in relation to this in #388, but the instructions directive is still not fully detangled.