Fixed bug: WPP Causes the WP page for Appearance->Themes->Customize to Auto-Reload

UD Forum topic:
https://usabilitydynamics.com/products/wp-property/forum/topic/wpp-causes-the-wp-page-for-appearence-themes-customize-to-auto-reload/
Fixed bug in [property_attribute] shortcode

UD Forum topic:
https://usabilitydynamics.com/products/wp-property/forum/topic/attribute-shortcodes-stopped-working/
Merge remote-tracking branch 'upstream/development' into development
Added define WPP_DEBUG_MODE to cron.php

It adds ability to use debug mode on cron job.
Example:
php -q {path} do_xml_import fa0d73f21f7e652bc7b63a04534e4107 debug_mode
Added FEPS 2.0 compatibility with specific themes
Merge pull request #4 from pemaxim/development

Bugs fixes and FEPS 2.0 compatibility