Change case of the unit "bit" from "Bit" to "bit" in web UI

Change case of the unit "bit" from "Bit" to "bit" in web UI

The correct case for "kilobit" is "kilobit", not "kiloBit".
And the same applies for Mbit, Gbit etc.
Reference is https://en.wikipedia.org/wiki/Kilobit

This commit changes the texts used in the web UI, so
that it correctly displays as "bit", "kbit", "Mbit" etc.

This fixes bugzilla item 10918.

Signed-off-by: Alf Høgemark <alf@i100.no>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>