Issue #208 - On the fly TMX

Almost done, just need to rewrite the tests for the new TMX function and delete the old one.

Added error/success messages and split the code in two views.

@tx2z , does the UI looks good to you?

![1](https://cloud.githubusercontent.com/assets/1294206/3022488/8ba8d4a4-dfc9-11e3-906e-f272033136f5.png)
![2](https://cloud.githubusercontent.com/assets/1294206/3022489/8ba9eb14-dfc9-11e3-8e8b-219d9db70ae2.png)
![3](https://cloud.githubusercontent.com/assets/1294206/3022490/8bab231c-dfc9-11e3-821e-227ed37c0c67.png)

I know it's an edge case, but I still think we need to check if ```file_put_contents``` fails. Something like
```php
if ($content) {
	$empty_TMX = false;
	try {
		$created_TMX = file_put_contents($target_file_path, $content);
	} catch (Exception $e) {
		$created_TMX = false;
	}
} else {
	$empty_TMX = true;	
}
```
And then manage ```$empty_TMX``` in the view.