Update de_DE.lang

Updated to equal latest en_US.lang file. Also, small translation and spelling fixes.
Create ko_KR.lang
Update language_tree.cfg

Added Korean (ko_KR).
Merge pull request #99 from kippie408/patch-2

Update language_tree.cfg
Merge pull request #97 from Vexatos/patch-1

Update de_DE.lang
Update de_DE.lang
Merge pull request #100 from ReneMuetti/patch-9

Update de_DE.lang
Update zh_CN.lang
Update zh_TW.lang
Update de_DE.lang

- Minor writing correction
- updated german translation for one-way tracks to be more understandable and less google-translator like
Update Russian translation
Merge pull request #103 from VeryBigBro/patch-6

Update Russian translation
Merge pull request #102 from misssalad612/patch-5

Update zh_TW.lang
Merge pull request #101 from Glease/patch-1

Update zh_CN.lang
Merge pull request #98 from kippie408/patch-1

Create ko_KR.lang
Merge pull request #104 from VirusSE/patch-1

Update de_DE.lang
Update zh_TW.lang
Merge pull request #105 from misssalad612/patch-6

Update zh_TW.lang for 7.3.0.0
Rename sr_RS.lang to sr_SP.lang
Merge pull request #106 from Zmiko/master

Fixed Serbian localization.