Update images for the chapter 2 and 5
Merge pull request #36 from lionel-m/chapter-4-rss
Update images chapter 5
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.
Custom module update

Typolight -> Contao
Links updated
Typo
...
Documented all email inserttags
Added base64 flags
Merge pull request #51 from Toflar/base64-flags
Merge pull request #50 from Toflar/email-inserttags
Merge pull request #42 from stefansl/patch-1
Minor grammatical corrections
Fixed invisible anchor tag