[connector] add hook point `*.pre`(cmd preprocessing) for bind

call bind callback function with ($cmd, &$args, $this, $volume)
on preprocessing exec any command.

ex.
```php
$opts = array(
	'bind' => array(
		'*.pre' => 'preprocessing'
	),
	'roots' => array(...)
);
function preprocessing($cmd, &$args, $this, $volume) {
	// You can change value of `$args`
	// Then, `cmd` is performed using changed $args.
}
[coonector] add new plugin "Normalizer"

elFinder Plugin Normalizer

UTF-8 Normalizer of file-name and file-path etc.
nfc(NFC): Canonical Decomposition followed by Canonical Composition
nfkc(NFKC): Compatibility Decomposition followed by Canonical

This plugin require Class "Normalizer" (PHP 5 >= 5.3.0, PECL intl >= 1.0.0)
or PEAR package "I18N_UnicodeNormalizer"

ex. binding, configure on connector options

```php
$opts = array(
	'bind' => array(
		'mkdir.pre mkfile.pre rename.pre' => 'Plugin.Normalizer.cmdPreprocess',
		'upload.presave' => array(
			'Plugin.Normalizer.onUpLoadPreSave'
		)
	),
	// global configure (optional)
	'plugin' => array(
		'Normalizer' = array(
			'enable' => true,
			'nfc'    => true,
			'nfkc'   => true
		)
	),
	// each volume configure (optional)
	'roots' => array(
		array(
			'driver' => 'LocalFileSystem',
			'path'   => '/path/to/files/',
			'URL'    => 'http://localhost/to/files/'
			'plugin' => array(
				'Normalizer' = array(
					'enable' => true,
					'nfc'    => true,
					'nfkc'   => true
				)
			)
		)
	)
);
```
Merge branch '2.1' into 2.1_n