Generic PHP plugins and config system 0.85

PHP plugin meta data specification can be utilized in multiple ways, especially just for human-friendly .php script descriptions. So the following implementation is just one possible way to utilize the plugin meta data scheme.
Generic PHP plugins and config system project has is GNU GPL / PD dual-licensed.
Main features:
- Read meta infos from .php plugins.
- Present them in a nice UI, which allows to enable/disable plugins.
- Non-destructively edit a "config.php" settings script.
- Resolve plugin dependencies.
Enhancements:
- A few changes in libconfig now provide better plugin dependency resolution.
- Default values for configuration settings are taken into account better, and so variable assignments get added less often.
- The plugin meta data reading now detects and converts the old WordPress plugin description format.