Update German translation

Updated German translation of strings.xml:
- Added all missing strings
- Improved some old strings to make their meaning more clear
- Added support for Basic Version of the mobile site (called it "Minimale Version")
  
  
Hi @velazcod, I updated the German translation to v1.5.

I think it should be noted that I changed the German "txt_about" a bit, so it is more readable in my opinion. My new translation would resemble the following text in English (assuming you don't speak German, I translated the changes back to English):

"""
Developed by Daniel Velazco.
velazcod@gmail.com
http://www.danvelazco.com

Source code:
https://github.com/velazcod/Tinfoil-Facebook

This app is for those people who require a Tinfoil Hat ([reference to english word "tin foil hat" here]) for Facebook. It creates a sandbox (an isolated environment without access to personal data, e.g. your address book), in which facebook\'s mobile site runs. [No more "INTERNET permissions" declaration here, because it is a bit obvious]

Coarse location permissions are only used if you activate \"Allow Check-ins\" in the preferences.

If you are skeptical about it, feel free to check the source code listed above. [changed order of the last two sentences here]
"""

The statements in "[ ]" brackets are comments that are not inside the actual translation, but which try explain my changes.

If you disagree with anything, please leave a comment below and I will modify it.

May I ask btw. how many active Play Store registered installs of Tinfoil with German locale there are? (You can see this somewhere in your Developer Console, I think.)