Render conditions

For #194
Documentation:

```yml
conditions:
  type: and
  callbacks:
    - ['function_callback', [a1, a2, a3]]
content: '{{ "markup string" }}'

conditions:
  type: or
  callbacks:
    - [['SomeClass', 'method'], [a1, a2]]
    - '@some_service:method'
function: 'render_something'

conditions:
  type: xor
  callbacks:
    - [ '@some_service:method1', ['#node', 'hello', '#entity_type'], 'true']
    - '@some_service:method2'
template: '@some_module/templates/block/hello_template.html.twig'
```