Bump vault version to 2.5.0 [wip]

Make U2F work with vault 2.4.0 changes

Switch from resin to balenalib

Improve the admin account warning.

Grammar fixes to README.md

Add Kubernetes deployment reference

Update PROXY.md

Removed: `include conf.d/proxy-confs/proxy.conf;` lines because they're specific to user (shauder) and will break nginx if copy-pasted/don't exist.
Changed: Moved listen value and server_name to top as is standard for nginx configs
Changed: Commented out SSL config as it's specific to user (shauder) and will break if copy-pasted/don't exist. But is still useful and a good idea for simplifying nginx config.
Changed: Rearranged location blocks because OCD. First /, then /notifications/hub, then /notifications/hub/negotiate because it looks nicer in a tree where each location grows.

Accept PUT and POST on /settings/domains, returns JsonResult, fixes saving Custom Equivalent Domains

Accept PUT and POST on /settings/domains, returns JsonResult, fixes saving Custom Equivalent Domains

Fix /sync without query string

Don't send Domains if excludeDomains=true on /sync

refine backup instructions

as mentioned in https://github.com/dani-garcia/bitwarden_rs/issues/223

Disable WebSockets negotiation by default