backport 44936fd to other language and pdf

This change needs to be backported to all languages. The pdf toolchain
processes this formula with a transformation to some latex mathematic
typesetting and therefore needs to be updated.
Update 01-chapter3.markdown
Fix typo ä->a

This changes:
"Stattdessen *erfässt Git" -> "Stattdessen erfasst Git"
Merge pull request #722 from konradkonrad/patch-1

Fix typo ä->a
Typo fix.
Typo fix.
[ja] Fix translation on improvements in the Git UI

The Japanese translation implies that all systems have had improvements
in their UI over the past few years, but many aspects of Git are still
hard to use. This is not in agreement with the original English:

"In the last few years, the UI has been refined until it’s as clean and
easy to use as any system out there; but often, the stereotype lingers
about the early Git UI that was complex and difficult to learn."

Change the Japanese translation to more closely reflect the English,
i.e.: that the Git UI has improved, but its image as a hard-to-use tool
still lingers.
Merge pull request #723 from wakeup/master

Typo fix and minor updates.
Merge pull request #724 from modocache/ja-internals

[ja] Fix translation on improvements in the Git UI
Merge branch 'fix_math_typeset'
fix mis-translation private<-->public

 public.key is "公開鍵" and private.key is "秘密鍵" in Japanese.
[it] updated chapter 3
[it] Chapter 2: Reviewed 'Getting a Git Repository'
[it] Reviewed "Cloning an Existing Repository"
[it] Reviewed "Recording Changes to the Repository"
[it] Reviewed "Checking the Status of Your Files"
[it] Reviewed "Tracking New Files"
[it] Reviewed "Staging Modified Files"
[it] reviewed "Ignoring Files"
[it] Chapter 2

Reviewed "Viewing Your Staged and Unstaged Changes"