Update multiple servers at once

[smcclennon]

Is your feature request related to a problem? Please describe.
Servicing multiple servers with pluGET requires swapping out or editing of configuration files and then re-running pluGET.

Describe the solution you'd like

1. Use the server address as the YAML key and indent all of its connection options under that key in the config file
2. If more than one server is defined in the config file, upon entering a pluGET command such as update all, all server hosts should be printed and the user should be asked which servers to apply the command to. User input examples: 1 for server 1. 1, 3 for servers 1 and 3. 1-3 for servers 1, 2 and 3. 1,4-6 for servers 1, 4, 5 and 6.

Configuration example:

Remote:
  host.com:
    Port: 21
    Connection: ftp
    Username: foo
    Password: fh29d
    SeparateDownloadPath: true
    PathToSeperateDownloadPath: /plugins_pluGET
  play.differentserver.net:
    Port: 22
    Connection: sftp
    Username: bar
    Password: 29fna
    SeparateDownloadPath: false
    PathToSeperateDownloadPath:

I have not included Local in this configuration example as I haven't used and don't understand how it works.

Describe alternatives you've considered
Multiple config files, one for each server. pluGET detects them all on startup and asks which ones to use. User input is the same as the previous solution, except numbers correlate to configuration files instead of servers.