Update de_DE.lang

Some small spelling corrections.
Hint: First letter of a name (also item and block names) should be capitalized!
Hint2: oneway track means oneway track, so "Einwegschiene". But for track.detector.direction and track.gated.oneway "Fahrtrichtung" fits better.
Merge pull request #107 from Vexatos/patch-2

Update de_DE.lang