custom appview setting #22

• ports the custom-appview branch of deer. includes a new persisted setting in the deer (experimental) settings page, and also a new environment variable to set the default appview did
• ports my own unproxy preferences which is needed for custom appviews to work as explained in this thread

i have only tested it on web. it works on web

i had to diverge from the deer custom-appview branch a bit because the original way of switching out the proxy no longer works so i had to add even more proxy overrides