Separate code and add extension points

[redneck-f25]

For further improvements we should separate the code into separate files. Do you agree?

Especially for my use case I need extensions points to hook into the core. Later, I'll drop a note about this.

[redneck-f25]

@dreampuf I want use GraphvizOnline as a transparent lightweight viewer for .gv/.dot files. That's why the index.html should be as small as possible.

There is a directory with mod_autoindex and RewriteRule as below.

RewriteCond %{QUERY_STRING} !(^|&)raw=?(&|$)
RewriteRule \.(dot|gv)$ /GraphvizOnline/index.html [END]

Furthermore, I need to manipulate the SVG before it is rendered (i.e. add a CSS stylesheet) and I need to generate the DOT code from other formats and write the result to the editor.

[dreampuf]

This is something I haven't done because of historical issues. Thanks!