Create language.de_DE.js

[herrhartmann]

Added de_DE Translation

[OleVik]

In regards to the grade-modifier used for scoring, this is a point of contention. The current implementation only uses it in the calculation of the SMOG-formula, and in the age/grade-requirements between localities. As such the simple addition to the SMOG-score is the first grade or late preschool leading into the first grade. From Wikipedia on Education in Germany this would be between 5-7, though I've opted for the lower bound for the US and Norway.

I would like to resolve this by improving the calculation across localities, but I'm not sure which standard would be best to apply to normalize these grade-levels across countries. The current implementation of the formula, and interpreted statistics is thus rather naive, and I'm very open to suggestions for improving them.