review backend dependencies

[tormath1]

Similar to frontend, let's take a moment to seat and review the backend dependencies. I've seen quite a lot of non-standard dependencies, used for one thing, that could be easily removed or implemented on the Nebraska side.

E.g: https://pkg.go.dev/github.com/labstack/gommon/log ("WORK IN PROGRESS")

$ go mod why github.com/labstack/gommon/log
# github.com/labstack/gommon/log
github.com/kinvolk/nebraska/backend/cmd/nebraska
github.com/labstack/gommon/log

This is for security and maintenance concerns.

[tylerauerbeck]

Somewhat related #1122 - looking at the current usage of go-bindata as it hasn't seen updates in some time and may be better served by native embed functionality.