add web resource files

src/main/webapp/com/ardublock/reference/404.html

src/main/webapp/com/ardublock/reference/_Logo_LGI_page.png

...n/webapp/com/ardublock/reference/_inhaltsverzeichnis.html

...in/webapp/com/ardublock/reference/_seitenformatierung.css

src/main/webapp/com/ardublock/reference/abs-beispiel.png

src/main/webapp/com/ardublock/reference/abs.html

src/main/webapp/com/ardublock/reference/abs.png

...main/webapp/com/ardublock/reference/addition-beispiel.png

src/main/webapp/com/ardublock/reference/addition.html

src/main/webapp/com/ardublock/reference/addition.png

src/main/webapp/com/ardublock/reference/and-beispiel.png

src/main/webapp/com/ardublock/reference/and.html

src/main/webapp/com/ardublock/reference/and.png

src/main/webapp/com/ardublock/reference/code_comment.html

src/main/webapp/com/ardublock/reference/code_comment.png

...ain/webapp/com/ardublock/reference/code_comment_head.html

...main/webapp/com/ardublock/reference/code_comment_head.png

...ain/webapp/com/ardublock/reference/constrain-beispiel.png

src/main/webapp/com/ardublock/reference/constrain.html

src/main/webapp/com/ardublock/reference/constrain.png