use notice container for all messages

- renamed error-container.php to notice-container.php
- add right CSS class to notice id depends on parameter
added message container to global setttings page
add timer on notices blink mode
Ajax requests mecanism #4

- ajax hooks declared in
[slideshare-posts-import](https://github.com/Spoon4/slideshare-posts-imp
ort/blob/master/slideshare-posts-import.php)
- added
[JSONEncoder](https://github.com/Spoon4/slideshare-posts-import/tree/mas
ter/includes/class-json-encoder.php) class
call get_user_slidewhows API service with AJAX #4

- added [javascript
handler](https://github.com/Spoon4/slideshare-posts-import/blob/master/a
dmin/assets/js/admin.js) to create and execute the request
- refactored
[displayNoticeContainer](https://github.com/Spoon4/slideshare-posts-impo
rt/blob/master/admin/views/error-container.php#L4) function
- changed nonce value on import page
add blink parameter on admin global settings page