Fix a bug related to view vary detection

1. Fix a bug related to view vary detection that caused first visit not cacheable.
2. Avoid warning if CURLOPT_SSL_VERIFYSTATUS option not available in old library during CLI purge.

Fixed PHP 7.3 compatibility issue

Fixed PHP 7.3 compatibility issue where error Serialization of Closure is not allowed

Allow CustomVary and Guest Mode

Added support for CustomVary.
Added Guest Mode to allow serving first visit from cache, then refresh to show the proper varied copy from cache.
Added logging backtrace of purge events to help debug unknown cause of purges.

Remove module version dependency

Remove versions from composer.json to work with latest 100.3.* framework.

Add missing purge event after reindex

add "clean_cache_after_reindex" purge event for reindex by schedule. Reindex will now properly trigger purged tags.

Fix compatibility issues with Magento 2.2.x

This release fixed some errors showing on Magento 2.2.0 and 2.2.1. Basically dependency on \Magento\Framework\HTTP\ZendClientFactory got removed.

1. Fixed an exception showing on cache management screen by replacing \Magento\Framework\HTTP\ZendClientFactory with \Magento\Framework\HTTP\ClientFactory.
2. Fixed an exception logged on cache backend selection.
3. Shell purge handling now uses \Magento\Framework\HTTP\ZendClient directly instead of ZendClientFactory.

Fix Admin session timeout when module installed

Fixed admin session timeout issue when LiteMage module is installed.
Fixed cache wrong copy when there is cache vary change, like change in currency.

Add CLI mode for FlushCacheByTags

Fixed exception when FlushCacheByTags event triggered from command line. Now this event can be handled in CLI mode.

Fixed static file 404 pages exception

1. move the HTTPPurgePlugin to frontend and adminhtml instead from global. Global scope will intercept static.php 404 process, and cause exception.
2. remove server_ip for 127.0.0.1, this will break in shared hosting setup. This should be configurable in future.

Display LiteMage Cache Statistics

Showing LiteMage Cache Statistics and plan option on Cache Management screen.