* new abstraction around storage
* re-work completely to fit new acme package pre-solving paradigm
* vault storage plugin
* add some vendor
* delete old vendor pinning mechanism
This:
* adds a global -v flag for verbosity
* refactors the "printer" package to have a DefaultPrinter and package
functions that call it, similar to net/http's DefaultServeMux
* adds printer tests
* moves current users of Debugf to Printf
* moves most users of the "log" package to use "printer"
* demotes noticably noisy log messages to "Debugf", like "IGNORE"-
and "NO_PURGE"-related messages
* Manual rebase of get-certs branch
* fix endpoints, add verbose flag
* more stable pre-check behaviour
* start of docs
* docs for get-certs
* don't require cert for dnscontrol
* fix up directory paths
* small doc tweaks
