Add extra validation steps

[hoangtrvu]

Before actually starting the migration process, Migration Helper can perform a number of validation as prerequisite checks:

• zat validate --path /path/to/v1_app should pass. The original app should be a valid V1 app.
• frameworkVersion in manifest.json must be less than 2.0.
• marketingOnly in manifest.json must not be true.
• Original app should not be requirements-only app.
• Any other specific conditions required for migrating V1 app to V2 app.