`ionic cordova ...` commands could check if `cordova` is installed first

Running `ionic cordova platform add android` on a node install without Cordova installed:

```
λ ionic cordova platform add android
> ionic integrations enable cordova
√ Downloading integration cordova - done!

? The config.xml file exists in project. Overwrite? Yes

? The resources/ directory exists in project. Overwrite? Yes
create config.xml
create resources
create resources\android
create resources\icon.png
create resources\ios
create resources\README.md
create resources\splash.png
create resources\android\icon
create resources\android\splash
create resources\ios\icon
create resources\ios\splash
create resources\android\icon\drawable-hdpi-icon.png
create resources\android\icon\drawable-ldpi-icon.png
create resources\android\icon\drawable-mdpi-icon.png
create resources\android\icon\drawable-xhdpi-icon.png
create resources\android\icon\drawable-xxhdpi-icon.png
create resources\android\icon\drawable-xxxhdpi-icon.png
create resources\android\splash\drawable-land-hdpi-screen.png
create resources\android\splash\drawable-land-ldpi-screen.png
create resources\android\splash\drawable-land-mdpi-screen.png
create resources\android\splash\drawable-land-xhdpi-screen.png
create resources\android\splash\drawable-land-xxhdpi-screen.png
create resources\android\splash\drawable-land-xxxhdpi-screen.png
create resources\android\splash\drawable-port-hdpi-screen.png
create resources\android\splash\drawable-port-ldpi-screen.png
create resources\android\splash\drawable-port-mdpi-screen.png
create resources\android\splash\drawable-port-xhdpi-screen.png
create resources\android\splash\drawable-port-xxhdpi-screen.png
create resources\android\splash\drawable-port-xxxhdpi-screen.png
create resources\ios\icon\icon-1024.png
create resources\ios\icon\icon-40.png
create resources\ios\icon\icon-40@2x.png
create resources\ios\icon\icon-40@3x.png
create resources\ios\icon\icon-50.png
create resources\ios\icon\icon-50@2x.png
create resources\ios\icon\icon-60.png
create resources\ios\icon\icon-60@2x.png
create resources\ios\icon\icon-60@3x.png
create resources\ios\icon\icon-72.png
create resources\ios\icon\icon-72@2x.png
create resources\ios\icon\icon-76.png
create resources\ios\icon\icon-76@2x.png
create resources\ios\icon\icon-83.5@2x.png
create resources\ios\icon\icon-small.png
create resources\ios\icon\icon-small@2x.png
create resources\ios\icon\icon-small@3x.png
create resources\ios\icon\icon.png
create resources\ios\icon\icon@2x.png
create resources\ios\splash\Default-568h@2x~iphone.png
create resources\ios\splash\Default-667h.png
create resources\ios\splash\Default-736h.png
create resources\ios\splash\Default-Landscape-736h.png
create resources\ios\splash\Default-Landscape@2x~ipad.png
create resources\ios\splash\Default-Landscape@~ipadpro.png
create resources\ios\splash\Default-Landscape~ipad.png
create resources\ios\splash\Default-Portrait@2x~ipad.png
create resources\ios\splash\Default-Portrait@~ipadpro.png
create resources\ios\splash\Default-Portrait~ipad.png
create resources\ios\splash\Default@2x~iphone.png
create resources\ios\splash\Default@2x~universal~anyany.png
create resources\ios\splash\Default~iphone.png
√ Copying integrations files to project - done!
[OK] Added cordova integration!
> cordova platform add android --save
'cordova' is not recognized as an internal or external command,
operable program or batch file.
[ERROR] Exception: Command not found: cordova
```