Adds a new `key_type` option to the Vagrantfile ssh configuration. It
defaults to :auto which allows auto detection of key type to use.
Otherwise it can be set to an explicit type supported by Vagrant.
Recent versions of OpenSSH remove support of ssh-rsa key types and host
key algorithms from the default conection configuration. Set options to
enable them and provide a configuration option which can disable them if
required.
Fixes various capitalizations in the docs
* Ex: VMware, Linux/Unix, PowerShell, some abbreviations
Also, Prettier auto-formatted away some trailing spaces.
