PHP Autoloading with namespaces: Load classes mapping namespaces to directories

Loader class
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Loader class allows you to create many classes with autoloading function based on namespaces.

__!!!__
__IMPORTANT__: This loader class is based on directory=namespace system, so if you define your class namespace as:

    namespace this\is\my\stuff;

Class should be located in directory:

    [include path]/this/is/my/stuff/

__!!!__

1. Parameters
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    * string[] $_includePaths - there are stored all user-defined include paths, as array of string (the best practice is to store absolute paths),

    * string[] $_fileExtensions - there are stored all user-defined class files extensions (like .php, .class.php, etc.),

    * string[string] $_loadedClasses - there are stored all already loaded classes, so they won't be loaded again (by the same loader instance) they are stored as [class name] => [class file path].

2. Methods
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    * _Loader_ setIncludePath(_string_ $path[, bool $prepend = true]) - use this to set a new include path. Include path should be path to directory, where class files are located. You can also decide if new path should be appended or prepended (second parameter). Function returns current Loader class instance (for chaining),

    * _string[]_ getIncludePaths() - use this to check out which directories you have already set,

    * _Loader_ setFileExtension(string $ext[, bool $prepend = false]) - use this to set a new class file extension. There's a second parameter, which works just like in _setIncludePath()_ function. Function returns current Loader class instance (for chaining),

    * _string[]_ getFileExtensions() - use this to check out which class files extensions you have already set,

    * _Loader_ load(string $className) - this is autoloading function (executes when some function is called). You can use this also manually, giving name of the class you want as the parameter,

    * _Loader_ register() - registers autoloading function. Autoloading is available AFTER this function is called,

    * _Loader_ unregister - unregisters autoloading function. Disables autoloading AFTER this function is called.