Improvements to Instagram Plugin, Only get newests posts and only get friends every two days.
Merge pull request #1840 from gbrady92/1776-instagram

Improvements to Instagram Plugin.

TODO: Set the plugin options namespace to 'plugin_options-#id#' with code like this:

$plugin_id = $plugin_dao->getPluginId('instagram');
$friends_last_updated = $option_dao->getOptionByName(OptionDAO::PLUGIN_OPTIONS.'-'.$plugin_id, 'last_crawled_friends') ;