Port Integration Migration submodule to Drupal 8

[ademarco]

Scope

In the scope of porting the Integration module to Drupal 8 we can start by porting only the submodule "Integration Migrate" first.

The Integration Migrate module only exposes a Migrate plugin to import for the JSON format specified here: https://github.com/nuvoleweb/integration/wiki/1.-Data-exchange-format

Tasks

• Create a new branch 8.x-1.x
• Remove all 7 code :)
• Create an empty Integration module, it will function just as a placeholder
• Start porting Integration Migrate module placing it under integration/modules/integration_migrate
• Test migration both via unit tests and Behat

[haringsrob]

Gotta add some more tests:

• More field types
• ??