Filters, ASCII field names and checkboxes

Source modifications:

• LOAD: filters via autoload classmap instead of require_once. Should fix errors when added to frameworks.
• FIX: convert ASCII object names to utf-8 while parsing definitions
• ADD: custom checkbox parser (opt-in mode)

Changes to folder structure:

• MOVE: app files to src directory.
• KEEP: top level fpdm.php as entry point / wrapper for all who do not use autoload files.

go for composer

Add bugfixes, autoload ability and php 7.x compatibility to original 2.9 release.

Untouched version 2.9

Contains the unchanged original source of version 2.9 as published on fpdf.org.

This won't work for autoloading (e.g. composer) without additional changes to the source code. Necessary changes will be released as versions 2.9.x