[elbe-devel] Add support for extended/logical partitions

[Philipp Rosenberger]

Adding support for extended/logical partitions for msdos hd images. Also
fixing a bug in the schema, wehere it was possible to create partitions without
labels.

Now it is possible to do somthing like this:
<msdoshd>
    	<name>hd.img</name>
    	<size>6GiB</size>
    	<grub-install />
    	<partition>
    		<size>2GiB</size>
    		<label>rfs</label>
    	</partition>
    	<extended>
    		<size>remain</size>
    		<logical>
    			<label>home</size>
    			<size>64MiB</size>
    		</logical>
    		<logical>
    			<size>remain</size>
    			<label>data</label>
    		</logical>
    	</extended>
</msdoshd>

The x86_64-pc-hdimg-gnome example has been extended to use a logical partition
as /home.

Best regards,

Philipp