Add Open Graph and Twitter card. Prepare to allow changing the Title using shortcode

Create default TOC style with options to use the theme css

Even in posts collections page, create the TOC as long as its in full post mode.

Allow to add TOC using shortcode (<!--toc-->). TOC add button in text editor.

Reverting it for compatibility with old theme.

The `$p->video` should return the video link only, to get the video ID we can use get_video_id(); and call it from the theme.

system/htmly.php
- Loads language files from folder lang/
- Sets language settings for date and time format
system/includes/dispatch.php
- function i18n() returns translated strings

Glob() is expensive so cache the category files.

The ported version of Twenty Fifteen and Twenty Sixteen include with the
package. Maintenance and bugs fixes.

Add category feature to the core.

Updated robots.txt + new htaccess files.

I made the following changes for the robots.txt and .htaccess files.

# robots.txt updated
- Allow theme assets (CSS, JS, Images, Fonts) for SEO
- Allow folder with uploaded images (/content/images)

# .httaccess files added
- /content - Deny all
- /content/images - Allow only jpg|png|gif
- /cache - Deny all
- /system - Deny all
- /system/admin/editor - Allow all
- /system/resources - Allow all
- /themes - Deny all
- /themes/blog/css - Allow all
- /themes/blog/fonts - Allow all
- /themes/blog/images - Allow all
- /themes/blog/js - Allow all
- /themes/clean/css - Allow all
- /themes/default/css  - Allow all
- /themes\default\img - Allow all
- /themes\logs\css - Allow all

Before this pull request, the 404 and 404-search templates where handled
as full HTML pages without the page context (layout).

With this pull request both pages are rendered inside the selected
themes layout. Additionally the 404 template now contains the "search
form" and the homepage link.

All Themes are already updated with the above changes.

This reverts commit 9fa8fab864.

Before this pull request, the 404 and 404-search templates where handled
as full HTML pages without the page context (layout).

With this pull request both pages are rendered inside the selected
themes layout. Additionally the 404 template now contains the "search
form" and the homepage link.

All Themes are already updated with the above changes.

Adding popular posts widget.

Trying to add content type: image, video, audio, link, and quote. No
styling yet.

Make HTMLy more flexibel.