use admin options credentials as default values for API requests
test type of js errorThrown ajax error param
compatibility for PHP 5.2
added description on import and post list pages
renamed WordPress Javascript global variable to avoid conflicts
added memory limit setting for import

PHP memory limit can now be modified from the import page
created class for ajax responses

to avoid multiple declarations of the generic method
`send_ajax_response`, a new `SlideShareAjaxResponse` class was created
avoid post duplication

- skip post import of a slideshow if a post with the same
`slideshare_id` exists
- display list of existing posts
removed unused comment
avoid launching import if no slideshows fetched
bug fix: syntax error
Merge branch 'master' into scheduling

Conflicts:
	admin/class-slideshare-posts-import-admin.php
	admin/includes/admin-ajax-hooks.php
	admin/includes/class-slideshare-importer.php
	includes/functions.php
	slideshare-posts-import.php