Show deprecation messages for things that will be dropped for 6.0.0 release

[Fatme]

OPTIONS

• platform template option
  --platfrom-template sets the platform template that will be used for the native application. It is a valid npm package, path to directory, .tgz or GitHub URL that contains a native Android or iOS template.
  As this option is a obsolete option that is no longer maintained, we decided to drop it for 6.0.0 release.

• syncAllFiles option
  --syncAllFiles option watches all production dependencies inside node_modules for changes. It triggers native rebuild if it is necessary!
  Webpack traverses the source code and collects all required modules, so this option doesn't make sense anymore.

RUNTIMES

As we have too legacy code for runtimes with versions lower than 5.1.0, we decided to drop the support for them as of NativeScript CLI v6.0.0. We highly recommend upgrading to the latest versions of the runtimes as we're planning to continuously update the min supported versions and of course to fully enjoy on the new features and fixes that are released with them.

• [Android] android runtime < 5.1.0
• [iOS] iOS runtime < 5.1.0

COMMANDS

• clean-app command

PLUGINS

• nativescript-dev-typescript plugin
• nativescript-dev-sass plugin
• nativescript-dev-less plugin

HOOKS

• shouldPrepare hook
• [Maybe] beforeWatch hook
• [Maybe] beforeWatchPatterns hook
• [Maybe] beforeLivesync hook

OTHERS

• [Maybe] warnings for deprecated short imports