Update images for the chapter 2 and 5
Add the sysinit hook.
Add sysinit to the list of hooks.
Rename the hook sysinit to initializeSystem.
Merge pull request #33 from tristanlins/3.0
Merge pull request #34 from lionel-m/chapter-4-newsletter-img-update
Update all links to version 3.1
Add the "initializeSystem" hook
Updated links to 3.1 branch on GitHub
Merge pull request #36 from lionel-m/chapter-4-rss
Added new Inserttag flags to Contao 3.1 documentation
Improved description of insert tag flags.

Added third column with link to external PHP function or additional
information for internal Contao methods.
Added english translation
Merge pull request #41 from Toflar/patch-1
Add a few corrections to the previous pull request
Use `target="_blank"` for links to php.net
Update 06-Data-Container-Arrays.md

Feld sql hinzugefügt
Update 06-Data-Container-Arrays.md

Feld relation hinzugefügt
Update 06-Data-Container-Arrays.md

Feld sql zur Konfiguration hinzugefügt.
Documented all email inserttags