Disk usage in loki adapter should report eMMC, and name SD better

[josephnobes-stfc]

The disk usage report works fine, but does not yet include eMMC (which will from now on always be present and formatted).

In addition, the names of the mounts when used directly are cryptic (for example the only thing differentiating SD and eMMC is a single number). Therefore, either replace them with friendlier names, or add friendlier names to the tree alongside the actual mountpoints.