Adding stats output to Renderers.

Had to add a container class for Renderer children (renderer-group-children) to apply the jQuery accordion to so that jQuery is not trying to collapse the stats `<ul>`.

Also added a "renderer-group-stats" class to contains the stats.
Adding total lines stat to `PHPAnalyzer`.
Adding filetype getter and comments regex abstract function to `AnalyzedFile`.

The new abstract `get_strings_and_comments_regexes()` function on `AnalyzedFile` fetches an array of regexes to be used when removing comments and strings.
Adding multiline flag to `AnalyzedFile`.

This flag is useful because it allows the regex to check if the thing we're matching is the first thing on a line when analyzing multiple lines simultaneously.
Adding base CSS analyzer and ThemeScanner.

The CSS Analyzer is an `AnalyzedFile` similar to `AnalyzedPHPFile` that applies a number of regular expressions to a CSS file.

The theme scanner takes some information from `AnalyzedCSSFile` and creates renderers from it to be displayed to the user.
Adding attributes display to renderers.

Attribute KVPs are now outputted above renderer stats.
Adding `renderer-group-empty` class to empty analysis tabs, and placing empty tabs at the bottom.
Fixing bug where renderer attributes would not be outputted if there were no stats.