Start implementing Trello API service

Implement name of system to import
Implement need validate data
Fix allowed system list
Start implementing Trello API service

Signed-off-by: Vitor Mattos <vitor@php.rio>

tests/unit/Command/BoardImportTest.php

@@ -58,7 +58,7 @@ class BoardImportTest extends \Test\TestCase {
 				['config']
 			)
 			->will($this->returnValueMap([
-				['system', 'trello'],
+				['system', 'trelloJson'],
 				['config', null]
 			]));