Rewrite 'react-native init' and 'react-native upgrade' without using Yeoman in preparation for templates support

Summary:
This is the manually imported version of facebook#10786

This was mostly straigthforward by replacing the local-cli folder with the version I had in my local git checkout,
plus a few other files I listed with git diff --name-only.

Reviewed By: hramos

Differential Revision: D4201118

fbshipit-source-id: 4d0fb54b0edda9de1abba427958e420fd2ac105c

Author: Martin Konicek

.flowconfig

@@ -2,8 +2,8 @@
 ; We fork some components by platform
 .*/*[.]android.js
 
-; Ignore generators because they are not real JS files
-.*/local-cli/generator/templates/.*
+; Ignore templates for 'react-native init'
+.*/local-cli/templates/.*
 
 ; Ignore the website subdir
 <PROJECT_ROOT>/website/.*

local-cli/__tests__/generators-test.js

@@ -36,7 +36,6 @@ export type Command = {
 };
 
 const documentedCommands = [
-  require('./android/android'),
   require('./server/server'),
   require('./runIOS/runIOS'),
   require('./runAndroid/runAndroid'),