Include media custom calendar in core pack when available

To test, install fa-IR (Persian).
Then create a new core package using fa-IR as language in the packages view
Download the package (for example: fa-IR_joomla_lang_full_3.3.3v2.zip)
![screen shot 2014-08-20 at 12 16 28](https://cloud.githubusercontent.com/assets/869724/3979326/28262a9e-2853-11e4-8190-fd588f46c442.png)

Uncompress the pack and then the site_fa-IR.zip:
The package will now include the necessary js folder in the site folder and the site install.xml will contain
```
	<media destination="fa-IR">
		<filename>index.html</filename>
		<filename>js/calendar-setup.js</filename>
		<filename>js/index.html</filename>
		<filename>js/calendar.js</filename>
	</media>
```

NOTE: remains to add the possibility in the package view to upload such a fa-IR folder in the media folder if not present (if feasible).