Rework strings for Eternus backend

Use SMI-S instead of SMIS in strings, and do not repeat ETERNUS
everywhere as it's visible in the UI that this is for this backend.
Reorder list of backends in UI

Put raw devices first, then sort drivers alphabetically, and then put
local file, and finally manual driver. This feels a bit less random.
Revert "webui: Add useless backend header in single-backend mode"

This reverts commit fbfb2e840b1ed34cf133a879763d2099a5fa511e.
webui: Avoid useless backend header in single-backend mode

This time, with a clean implementation.
Merge pull request #205 from vuntz/ui-bits

Fix SMI-S string and tweak order in backend menu