Support custom post types

• NEW: Ability to separately enable Factlink for all different post types.
• FIXED: Compatibility message with unsupported PHP versionn.

New admin functionality

• NEW: Factlink configuration panel
• NEW: Ability to enable Factlink for all pages and/or posts
• NEW: Ability to enable Factlink for single pages and/or posts
• NEW: Ability to replace Wordpress comments with Factlink