Added 'day after tomorrow' and support in German language

[harsh9200]

fixes #649

Added all missing German Language data.

After

>>> from dateparser import parse

>>> parse('day after tomorrow')
datetime.datetime(2020, 3, 29, 1, 28, 26, 11452)
>>> parse('übermorgen')
datetime.datetime(2020, 3, 29, 1, 28, 35, 192541)

>>> parse('two weeks ago')
datetime.datetime(2020, 3, 13, 1, 29, 3, 952504)
>>> parse('vor zwei Wochen')
datetime.datetime(2020, 3, 13, 1, 28, 46, 541678)

[codecov]

Codecov Report

Merging #650 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #650      +/-   ##
==========================================
- Coverage   95.21%   95.21%   -0.01%     
==========================================
  Files         302      302              
  Lines        2507     2506       -1     
==========================================
- Hits         2387     2386       -1     
  Misses        120      120              

Impacted Files	Coverage Δ
dateparser/data/date_translation_data/de.py	100.00% <ø> (ø)
dateparser/data/date_translation_data/en.py	100.00% <ø> (ø)
dateparser/date.py	97.96% <0.00%> (-0.01%)	⬇️

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