Fix AdImage::create() Exception type + fix php-doc

Summary: Fix AdImage::create() Exception type + fix php-doc

Test Plan: Try to create an image throuh AdImage::create() using a zip file
Adds CurlLogger to output curl commands from SDK requests

Summary: Using the CurlLogger will enable developers to easily see the calls being made in standard output, and can be used when reporting bugs.

Test Plan: Use the curl_log.php in examples, or a fun one is to change the logger used by tests and run!
Implement AbstractCrudObject::exportValue()

Summary: AbstractCrudObject::exportData() should be able to export arrays of AbstractObjects

Test Plan: run tests
RFC - Adding helper objects for object_story_spec in adcreative

Summary:
This diff creates a set of helper objects that map to the types of data needed when creating page posts using object_story_spec.
Take a look at the AdCreativeTest::testMultiProductObjectSpec() for how this actually works

Test Plan: run AdCreativeTest
Set comments in config.php.dist

Summary: Set comments in config.php.dist

Test Plan: read