Screening and fixing of translations.

There are some issues I was facing while skimming over the text.

 1. Is there a wiki which standardise phrases?
 2. I couldn't check for respecting the 80-chars-limit in poedit. Pay special attention to this!
 3. I didn't take care with comparing every string to the English counterpart in this iteration. However, some values seem outdated.
 4. Can you provide some context (e.g. in "notes to translators") for skipping the full stop sometimes?
 5. Why is there sometimes just "prints this help" and "print this help and quits"? (Context, please) Same holds true for version.

Here are some questions, I'd like to get answered to update this PR before merging:

 * world-Datei or World-Datei?
 * world-Set or world-Menge?
 * Set or Menge?
 * Files or Datei (see "Cachefile")
 * Primary translated as "Auftritt"?
 * Useflags or USE-Flags?
 * Buildtime or Build-Zeitpunkt?
 * Lineskip or Zeilenvorschub (actually that would be linefeed)
 * nichtausführlich or nicht-ausführlich?
 * Keyword in the meaning of Schlüsselwort or Suchbegriff?

Some final notes:

 * "vermöge" is outdated. Suggest a replacement, please (or I do)
 * what is this line with "node" (about :line 660) about? I didn't get the meaning
 * Environment is Umgebung, whereas sometimes I get the feeling, you mean PATH …

Please feel free to comment on certain lines what you think about.