Update README.md
Issue #165: Use render_cache key.
Issue #178: Add documentation to filter fields.
Merge pull request #165 from mateu-aguilo-bosch/165-cache-key

$plugin['cache'] is a reserved property, use "render_cache" instead.
Improves documentation.
Fix documentation error
Merge branch '7.x-1.x' into 181-access-origin

Conflicts:
	plugins/restful/RestfulBase.php
	plugins/restful/RestfulEntityBase.php
	tests/RestfulRenderCacheTestCase.test