Implemented door.
Javadoc fixes
Implemented Trapdoor
Versionsnummer korrigiert

Die Versionsnummer ist jetzt 4.0-SNAPSHOT
Javadoc y'all
Doors korrigiert
Javadoc geändert
Door & Trapdoor schöner gemacht
Door verbessert
...
Merge commit '70c8ddb55f7e53e6e57b9077c640c15678e6d0cd' into 4.0
Merge commit 'd2d4a77f671ac4c38e350b511c8725364926bc1f' into 4.0
Merge branch '3.5' into 4.0
Merge branch '3.5' of https://github.com/lfuelling/textie into 3.5